You guys seem to be spending a lot of time and energy focus on how many bars you have and speedtest. While helpful to see if you are experiencing major performance degradation you should really be focusing your energy on working with AppleCare support. This is what I am doing.
The best way to solve the problem is to work with AppleCare to get the baseband profile installed which enables debug logging for cellular.
https://developer.apple.com/bug-reporting/profiles-and-logs/
Then you will need to repro the issue and create a sysdiagnose which compresses a bunch of logs together. Then get these files over to support who then send the files to engineering. It is only then that engineering can finally take a look at the hard data and dig through 1000s of lines of logs to try and figure out what is the root cause.
Then after root cause is found then they can work on writing and testing a code fix.
Spend less time doing speed tests and more time working with AppleCare to gather logs to send to Engineering!