Should fact checkers be less stringent when fact checking Biden?

No, and there's been pushback on misstatements he's made.

Nope, fact check him as much as the last guy. If Biden's policies are any good, he will be able to tell the truth about them.

ALL politicians NEED to be stringently fact checked

Some will be found wanting far less than others although Trump has set the bar very high in that respect

They already do, that is, if they even bother.

Fact checkers were all burnt out after 4 years of Trump and needed a vacation. 

No one can operate at that pace for 4 years straight  and not burn out. 

Trumps every utterance needed to be fact checked. 

Since he has told 10,000 less lies than Trump had at this point in his presidency - it is like a vacation for them. 

Yes compared to con man Trump.

They're doing a great job. Are your panties in a bunch because there is very little negative news posted about Biden? 

He has been for many years. Enough already.

Well, they appear to believe in being less harsh with the mentally-challenged.