In my Post 574, I mentioned that the two knobs on the face-plate of the FIP, if broken, are simply unrepairable, but Oz Flyer (David) in the Comment suggested two possible solutions to repair them.  Here’s the first one I just tried since I don’t have a 3D printer as required in his second suggestion.

Stuffs needed are just some super glue and WD40, and I put everything on a piece of paper to avoid either the glue or the WD40 spilling over onto the table.
Firstly, spray a little WD40 into the shaft hole, and wipe clean the excessive.

Then dip a small amount of super glue onto a dental floss pick.

Transfer the glue to the broken tip inside the knob.

Put the knob and the broken shaft together thru the shaft hole as quick as possible, and press and hold them for a few seconds.
The knob is recovered.   Wipe out residues of WD40 if any.

It took me about 5 mins to fix the broken knobs on the two face-plates.

After that, assemble the face-plates back to the LCD modules.

The knobs are working normally again.

Thanks Oz Flyer !