Made it on FB 0.23.
The QB dialect does not store arrays in the same row order, like it's said in the manual. This is important in graphic multidimensional arrays.
Recently launched a program, that goes fine in Qbasic 1.0 and Pds 7.1. But in Fb,
DIM Z(100, 10) AS INTEGER
like 100 for graphics and 10 for animation frames,
PUT (X, Y), Z(0, frame)
PUT-s only small chunks like they are 10 elements' pieces. And sometimes even seeds the screen from the placepoint with garbage.
Relocating all references to PUT Z(frame, 0) made it right.
It'd be nice to have the same order as QB under fbc -lang qb, but I can't say how easy it'd be to implement this.