RSL SACCH FILLING are per TRX, not BTS scope
Contrary to the BCCH FILLING (which are BTS-wide in scope), the SACCH filling are actually only TRX-wide. This can already be seen by the message discriminator, which are TRX Management.
Despite that, OsmoBTS is storing the SACCH FILLING in a BTS-wide array, and not a per-TRX array.
This results in a situation where TRX 2 can overwrite the SACCH filling of TRX 0 or any other TRX, and in general only the last-set SACCH FILLING will prevail.
I currently cannot think of a [useful] situation im which different TRXs have different SACCH Filling, so this is a low-priority item. Please note that OsmoBSC cannot generate that anyway.