I have the same problem, but I thought it was film dependent:
I shoot TX and occasionally Delta 100.
I process TX in Emofin and occasionally in rodinal 1+100, and delta in Rodinal.
My SA-21 refuses to eat the delta, but TX is ok.
I have, thanks to Brian Puccio, another tested SA-21 on my way.
I will see in a few weeks how this one behaves.
Now that I read this thread, I will also probably try to process Delta in emofin and see if that changes anything.