Why does my GFI keep going off? Is it dangerous?
I am not a professional electrician but one possibility is failing component.  If yours are plug in (or if you are happy with mains wiring) then try swapping the two dodgy ones with each other or with non-dodgy ones.  Make sure you swap like with like (current/wattage ratings etc).  Make sure you take all necessary precautions. 

If the fault follows the component then it would point to a failed component.

If the fault doesn't follow the component but is on the same circuit then I would say there is something wrong with the install.  My top three issues are: water damage; rodent damage; or deteriorated installation.  Good luck trying to find it!

Water is notoriously nasty for troubleshooting and just because you found some at point B it isn't necessarily coming from point A (the closest source).  It could be coming from point R (a totally random point nowhere near).  It likes to follow the scenic route from source to where it manifests.

Yes it's dangerous! The GFI is there for a reason.  At least you have not said that you have forced it permanently on my taping it in the on position.  And that is not a suggestion.  DON'T DO IT!

Yes it could potentially cause a fire.  Especially if it is a fault in the installation.  It could be sparking unseen and sparks are a good source of fires.