@JimneyCricket 

It may well be that the algorithm is determining that the 4g is faster and more stable than the 5g.  I know personally where I live, we got 5g approximately 6months ago but its not as quick as the existing 4g network is, that will likely change in time.. but at moment 5g is slower.

The Settings 5g perferred just indicates that ideally use the 5g connection, unless 4g is better in some way.  Sounds like what is happening for you.   Phones wont do this, they prefer the newer, not always faster or as stable connection.

  @Philbert 

Meant to say,  another option would be to downgrade the firmware to the older one if you prefer that.  This can be done via the GUI web interface