No, the seed has stayed the same ever since I initialy started the world. The only changes were to the snapshot that i was using.
(I will however do more testing with some new worlds since my time has freed up and will let you know.)
I have found that my slime chunks have moved from versions 20w17a (in which the slime chunks matched that of 1.15.2) and 20w20b(also 20w21a though i needed to downgrade thanks to a structures bug). It looks like the slime chunks got completely rearranged during the snapshots. Using admist and an overlay client side mod i did confirm that the slime chunks did change. This is a shame bc i had already built two slime farms(dug by hand) : ( --These are no longer spawning slimes (chunk dug out) at all
I should add that there are no blocks above the spawning spaces and i can confirm that the client side mod (minihud by Masady) does not interfere with the game mechanics, it simply renders outlines for structures for the client.
It won’t go away but if you know how comment!
Upon loading up several test worlds between the snapshots(20w17a, 20w20b, and 20w21a) with all the same seeds, I have pinned it down to 20w21a as having changed the slime chunks. All the test worlds were the same seed, a quad witch hut seed (2628231886974071171) and i compared them using the same two chunks that i knew were slime chunks in 1.15.2 and 20w17a. In both 20w17a and 20w20b, the slime chunks were the complete same( and also 20w20b had the same layout of slime chunks elsewhere). However 20w21a's slime chunks were different. I tested these out both modded(using the overlay) and vanilla(by removing all blocks down to one layer of stone).Edit: I found the original cause of the issue^^, the world seed got reset to 0 upon switching snapshots for some reason (idk the fix for this), however below is still true though off topic
Let me know what files you would like me to attach(such as admist, screenshots, debug, etc) and I'll supply them.
As a side note when i generated the new world (same seed as before) in 20w20b a part of the mineshaft generated differently, outside of the mineshaft in a tree. I did not find this in the same seed generated in 20w17a(or the 20w21a one). As well the nearby village generated differently in both 20w20b and 20w21a from the one generated in 20w17a.