If you're getting problems like that with an R-XSR then I'd have to suspect that either there's something very wrong with how you have the antennas mounted on the quad or that the R-XSR is actually faulty. The fact that you have replaced one of the antennas suggests that you may have accidentally shorted something when soldering the new antenna to the receiver.

For FrSky, if your RSSI drops below 42, that's when you lose signal. Seeing as you're using an old version of Betaflight, the RSSI value displayed is in dBm, so you're right at the edge of losing the signal right from the start. The settings on my Taranis start warning about low RSSI at 45. At 43, the radio is shouting "turn back, signal loss imminent!".

To make sure that your R-XSR has failsafe set correctly, you should set your receiver failsafe bypowering up your quad and radio, then turning off the radio and pressing the button on the R-XSR. This will set failsafe mode to 'no output' which will be detected correctly by Betaflight as a failsafe.