The s20fe will not switch back to 4g ven when the 5g signal is weak. Cha nging settings in the networks menu will not lock the device to 4g. It will choose 5g no matter what you do.
Verizon cannot fix the issue. This began after the last update. Verizon refused to switch out my phone without me spending hundreds of dollars on a new device.
I found an app that sticks the phone in 4g. It's working very well. It's called forge 4g/5g only. Choose LTE and it keeps the phone on LTE. The phone has not moved to 5g one time since I set it up, unless I changed the settings.