The jailbreak has nothing to do with the stability of your version. It is just as stable as previous versions on my device and many others
You have a tweak that hooks into the phone app that crashes your phone
Do you have any voice recording tweak?
And make sure the tweaks you have installed are compatible with the firmware you're on
Otherwise, you may have to start removing suspecting tweaks until the problem goes away. The good (??) thing is that the problem is easily reproducible so you can test right after you uninstall a tweak or a few at a time to see if it's fixed
Better than those unreproducible at will problems (such as the mute switch problem from not too long ago). You just have to uninstall a tweak or a few at a time, leave it like that for a while (if in the next few days, the problem goes away, then you know those tweaks weren't the cause; however, it it happens again in the next few days, you'll have to test uninstalling other tweaks)