Frequent block lag and crashing

System Details –
Details:
Minecraft Version: 17w15a
Operating System: Windows 7 (x86) version 6.1
Java Version: 1.8.0_31, Oracle Corporation
Java VM Version: Java HotSpot(TM) Client VM (mixed mode), Oracle Corporation
Memory: 132026544 bytes (125 MB) / 259522560 bytes (247 MB) up to 259522560 bytes (247 MB)
JVM Flags: 0 total;
IntCache: cache: 0, tcache: 0, allocated: 12, tallocated: 94
Profiler Position: N/A (disabled)
Player Count: 4 / 20;