I can't reproduce this issue on Android.
I have this problem too after update to new version, (build 96 i think). My situation is like this: old version have a game saved and play for a while, update new version, get in, try armor conveyors, when i long press and slide, it successfully add 1 or 2 block, but the the map start sliding too, and i 1cannot add the new conveyors. Using diagonal is still the same. But I can still place the block 1 by 1. After save and quit and get back to the game (it loads again), start new custom game, no problem, load in the old save, no problem.
Ps android 8.0