Lost Signal To My Second Sim

[Bullettime]

A few days ago this occurred. At that stage I had CM13.1 running. I had not undertaken any new updates.
On Monday I was able to receive and make calls with both SIMs.
On Wednesday I noticed that the second sim wasn't showing up with a signal on the home screen.
Researched and checked the hardware which all came back as OK. I switched the sims into another phone and they work fine on them.
I am now on LOS 14.1 and still face the same issue.
I have noticed that if I toggle off or on the mobile data between phone providers this will allow phone signal to be established, but I lose the signal in the other sim
has anyone experienced anything similar in the past?
If so, would anyone be able to assist in resolving this issue?

 

[schoeny]

Maybe the contact to your sim is interrupted. So it happend to me. I made a little paper with tape under the sim to get it pressed in the slot. So just have a try, if it is the same "hardware problem"....