Two things mentioned by few railway employees on the issue with LHB. This is just their personal opinion
(1) Revision in coach composition (especially reduction in gen coaches) which has led to more wl/gen passengers in SL coaches
(2) Big issue with bio toilets. Can only be cleaned/chokages removed in stations where PM happens and cannot be done by OBHS or any station on route
But...
more... since safety is a top priority for railways hence the project to only produce LHB coaches henceforth