Help with battery charge surge

[RenoRock]

We currently have:
Powermax boondocker converter
2- NAPA 6v batteries, have had these abour 4 months.
PMI EMS HW50C power monitor system
trimetric power monitor.
2000i honda gen

While dry camping, we started up the gen to charge the battery. After an hour or so the gen, running in econ mode, starting surging back and forth from high to low as if the load was constantly changing.
After checking the generator, my next step was to check the power monitor. I noticed the amps in were ranging to from the 50s to the 10s back and forth. The voltage was moving too, from 12.2 or so to about 13.4.
Back on ground power we haven't seen the surge, but then again we may not have been looking for it since we didn't get the aural cues as when the generator is running.
Any ideas on what caused this and what we can do to troubleshoot?

Thanks in advance!

[Ditchooker]

open the vent on the fuel tank of the generator. I have forgotten to open it a couple times and it surges like mad when a vacuum develops in the tank. Probably the only time I ever hear it lol

[RenoRock]

That was actually my first check. Didn't make a difference. Turned off the gen for a while, Turned it back on later. Ran fine, but went to cycling with electrical load again. Turned off ECON, gen ran steady, but amps still surging.