I don't have this issue on any earlier Minecraft versions, but on 1.14, 1.14.1, and 1.14.2, if I set off TNT and then destroy the blocks on the fringe of the explosion after the blast happens, the game framerate will hitch badly with every block break and block placement in that area. On top of that, torches cause large hitches too on placement in dark areas and if I place or break blocks around the torch. Turning on simple lighting does not fix this. Output log gives zero errors or any indication that anything whatsoever is wrong even when turning on the debug messages, Tested this on another desktop with the exact same results. Exact same lag experienced. Same lag also experienced on Pre-Release 4 of 1.14.3.