A similar issue. However, I don't understand why fillet is having issues with the R, especially since I have managed to fillet the other letters just fine. The odd thing is that I have managed to get fillet to react once, but never after using the same radius.

I have attached the scene.

hi maybe a little trick
I have scaled x 10 the entiere model then made the fillet 0.2

I have not made the fillet base on this picture, but the fillet works also for the base!
(file 3Dm linked with base ;) (not unscaled / 10 !!! )

So you can "unscaled" / 10 at the end ;)
So I believe you work at a too little size scale of project unity ;)

thank you very much. That solved the issue :)
Now i can finally finish the model :D