This is the list of already known bugs in VCMI 0.5x. Please don’t report them.
Hero placeholders (object ID 214) are not handled correctly and may cause crashes on map reading (but I don’t see any reason why anyone should place them on normal maps…)
Wrong creature growth’s icons in the Conflux
Pathfinder on bigger maps can cause lags (but since 0.53 it’s much better)
Sometimes there are displayed wrong town graphics on map (e.g. without fort)