Hi Andrey,
For now you can add $ suffix to make it work, i.e.
=if(find(wcol(j)[L]$, "mm.tif") > 0, "CS", if(find(wcol(j)[L]$, "_0.00deg.tif") > 0, "XZ", if(find(wcol(j)[L]$, "_90.00deg.tif") > 0, "YZ", "???")$)$)$
PS, as previous reply told, we still recommend to use This instead of wcol(j) in cell formula.