Instead of upgrading 3.7.2 to 3.8.1, better write 3.8.1 image to a spare microSD card, slip-out old microSD card and slip-in the spare microSD card. See configuration steps here:
Howto : Piaware SD card image 3.8.0 Quickstart Guide
Using a spare microSD card for fresh install has advantage that in case of any problem with fresh install, you can replace new card by old card and your system will be up again.
On new card you should make a fresh install of FR24 feeder. I don’t foresee any problem in doing so. I have done it innumerable number of times.
First note down your FR24 feeder key either from file /etc/fr24feed.ini
in existing install, or by logging in to your Fr24 account, and go to stats page, and find it there.
Next install fr24feed by the bash script. When you reach settings stage, do NOT
use setting receiver="dvbt"
. Use receiver=Beast (TCP)
and host 127.0.0.1:30005