[mrweasel]

I believe that Firefox is replacing some Facebook JavaScript with a stub, to avoid that sites break because some tracking bits are missing.

So the reason why the GA object is replaced, rather than removed, is because removing it would break other sites. Tee Spring is trying to do the right thing, but fail because other sites don’t do the same.

[gpvos]

Both uBlock Origin and TeeSpring are trying to do the right thing, but in incompatible ways. I would say in this case the onus is on uBlock Origin to provide a stub that is as transparent as possible.