Do they have the Bar Code module? There is an old unfixed bug of that era that bites you bad when choose Unattended Bar Code Transaction Import. Don't have to run it just choose it (actually don't). Choosing it writes an [I/MABCx] key to the BC0 file (table). That is the B/C Parameters file now has an unexpected and bad I/M options record in it. You're okay at that point until you restart MAS.
You may know that upon start up of legacy MAS, the options records for all modules are copied into SY0CTL. So once I stepped thru that code and saw it was copying GL, AP, AR, IM, etc - all of them had their module option keys copied into SY0CTL. Everything was fine until gets to BC. That's where it copies not only the [B/CABCx] keys but also the illegitimate [I/MABCx] key that got in there because you selected Unattended Bar Code Import earlier.
So the point is upon start up that bad I/MABCx from BC0 overwrites the good I/MABCx from IM0 and therefore it overwrites your I/M Setup Options. Fielded this call a bunch of times on MAS 200 SQL.
About the Next SO and Invc # , you might want to look at all the xx0 Options tables (except S/O) with DFDM to see if any of them erroneously have [S/OABCx] keys.