2 portals created in 1 stronghold

Cannot confirm. The stronghold is arranged differently when trying to reproduce.

Cannot confirm either, see screenshot.
In what version that world was created first ?

In 18w20c. I was looking for a good seed for speedrun, and I tested like 20 stronghold in 20 different seeds, when i saw this one. What is extremely strange is that the stronghold is different when im loading the same seed again...

Can you please take a look in the archived logfiles at the time you've created the world the first time ? Is there anything unusual (exception while generating structures etc)?

I delete the world like 2 mn after post this bug :/ (i couldnt know that the same seed would generate a different stronghold)

Maybe somehow im still able to look in the archived logfiles ?

I found a crash report when teleporting at this stronghold for the first time :

---- Minecraft Crash Report -------- Minecraft Crash Report ----// Shall we play a game?
Time: 19/05/18 18:01Description: Exception generating new chunk
java.util.concurrent.ExecutionException: java.lang.IllegalArgumentException: bound must be positive at java.util.concurrent.CompletableFuture.get(CompletableFuture.java:2237) at sj.c(SourceFile:129) at bbd.d(SourceFile:248) at bbd.l(SourceFile:243) at bbd.b(SourceFile:597) at ahz.a(SourceFile:1145) at arn.dj(SourceFile:336) at arn.R_(SourceFile:278) at sm.i(SourceFile:372) at tj.Y_(SourceFile:189) at hs.a(SourceFile:221) at ti.c(SourceFile:175) at net.minecraft.server.MinecraftServer.w(SourceFile:720) at net.minecraft.server.MinecraftServer.v(SourceFile:627) at dhr.v(SourceFile:156) at net.minecraft.server.MinecraftServer.run(SourceFile:532) at java.lang.Thread.run(Thread.java:745)Caused by: java.lang.IllegalArgumentException: bound must be positive at java.util.Random.nextInt(Random.java:388) at bze.b(SourceFile:177) at bze.c(SourceFile:214) at bze.a(SourceFile:32) at bze$p.b(SourceFile:336) at bze$d.a(SourceFile:833) at bvr$a.<init>(SourceFile:89) at bvr.a(SourceFile:61) at bvs.a(SourceFile:252) at bvs.a(SourceFile:80) at bxy.a(SourceFile:16) at bxy.a(SourceFile:13) at brv.a(SourceFile:27) at bbx.a(SourceFile:515) at bpi.a(SourceFile:109) at sy.a(SourceFile:12) at sx.a(SourceFile:34) at bpm.a(SourceFile:87) at td.a(SourceFile:59) at td.a(SourceFile:23) at agf$a.a(SourceFile:143) at agf$a$$Lambda$1462/31983799.apply(Unknown Source) at java.util.concurrent.CompletableFuture$AsyncApply.exec(CompletableFuture.java:501) at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:289) at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:902) at java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1689) at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1644) at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:157)

A detailed walkthrough of the error, its code path and all known details is as follows:---------------------------------------------------------------------------------------
-- Head --Thread: Server threadStacktrace: at sj.a(SourceFile:179)
-- Chunk to be generated --Details: Location: -30,-86 Position hash: -365072220190 Generator: brd@23041307Stacktrace: at sj.a(SourceFile:179) at sj.c(SourceFile:132) at bbd.d(SourceFile:248) at bbd.l(SourceFile:243) at bbd.b(SourceFile:597) at ahz.a(SourceFile:1145) at arn.dj(SourceFile:336) at arn.R_(SourceFile:278) at sm.i(SourceFile:372) at tj.Y_(SourceFile:189) at hs.a(SourceFile:221) at ti.c(SourceFile:175) at net.minecraft.server.MinecraftServer.w(SourceFile:720) at net.minecraft.server.MinecraftServer.v(SourceFile:627) at dhr.v(SourceFile:156) at net.minecraft.server.MinecraftServer.run(SourceFile:532) at java.lang.Thread.run(Thread.java:745)
-- Player being ticked --Details: Entity Type: minecraft:player (sm) Entity ID: 135950 Entity Name: Erisium_Bazippo Entity's Exact location: -471.50, 88.00, -1367.50 Entity's Block location: World: (-472,88,-1368), Chunk: (at 8,5,8 in -30,-86; contains blocks -480,0,-1376 to -465,255,-1361), Region: (-1,-3; contains chunks -32,-96 to -1,-65, blocks -512,0,-1536 to -1,255,-1025) Entity's Momentum: 0.00, 0.00, 0.00 Entity's Passengers: [] Entity's Vehicle: ~~ERROR~~ NullPointerException: null
-- Ticking connection --Details: Connection: hs@40cd601f
-- System Details --Details: Minecraft Version: 18w20c Operating System: Windows 10 (amd64) version 10.0 Java Version: 1.8.0_25, Oracle Corporation Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation Memory: 175205456 bytes (167 MB) / 1073741824 bytes (1024 MB) up to 1073741824 bytes (1024 MB) JVM Flags: 8 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=50 -XX:G1HeapRegionSize=16M Profiler Position: N/A (disabled) Player Count: 1 / 8; [sm['Erisium_Bazippo'/135950, l='New World', x=-471.50, y=88.00, z=-1367.50]] Data Packs: vanilla Type: Integrated Server (map_client.txt) Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.

Nice, that way you've confirmed my issue MC-129946 - which I created while testing this issue.
Maybe the crash caused the generation of the two portals ?!
But: Closing this ticket since it cannot be reproduced.

Why close if the bug is real ? Even if you can't reproduce this bug, it can happen to anybody right ?

Edit : by the way, i found an other bug : stronghold often doesn't generate, and sometimes the stronghold generation changes (chest loot, eye in portals) when generate the same world in the same snapshot (18w20c)

This underlying issue is MC-129946, that has to be fixed, then any side effects like dual portal or no stronghold at all will be co-fixed.