Yes, it can happen. My installation tester invariably trips a certain brand of RCBOs below 16A. It's one of those never ending battles where on one side RCD makers are trying to make their devices better/more sensitive/less error prone and on the other side instrument makers looking for ways of shoving a high enough current through them that they can get a half plausible measurement that's not swamped by noise or general variation in the supply. In the old days testers used a large d.c. current to deliberately blind RCDs so the test current went unnoticed, then we got A-type ones that can cope with and/or notice the d.c. and still trip.

If all else fails, it's just a matter of measuring R1+R2 and adding to a measured Ze (or Zdb) and then verifying (e.g. with a continuity meter) that the c.p.c.s have been reconnected properly.

   - Andy.

Hi Craig. Just a thought, 
Could you please specify the make and model of the tester you are using? Have you experimented with the 3-low and 2-low settings? In my experience with the Megger tester, the 2-low setting tends to avoid tripping, whereas the 3-low setting often results in a trip.