Googling, it seems to be a basic blowback style marker. Most likely cause is the hammer o-ring being worn (even a small nick in it can cause issues). Replace and lube it and it should be fine again.
Note - when you reinsert the hammer, it can catch on the trigger sear, damaging the o-ring. I find removing the trigger frame is the safest way to prevent this.
If you need any other advice on it, ty looking for maintenance info on spyder markers which are pretty much identical inside