My 2 or 3 previous phones have usually always had one of the numbers show as unknown to but I've never had an issue with it turning off. Have you been able to turn on the option Dual SIM Always option?
yeah I can turn that on though it seems it forwards calls from one to the other when one is unavailable which I'd like to avoid. I typically typically mute calls from my work phone after 5pm
Hmmm. I don't know really going to be honest. How about switching your work SIM to calls and messages and your personal SIM to mobile data and see if they both work that way.
One of the reasons for the unknown number not showing up is that the SIM with the unknown number has had its original number changed, so that could mean you've carried over an old number to that SIM.