Yes, your initial impression of low power is likely correct. In fact, the standard recommendation when low on power is to lower one jack at a time. I would not assume because you are on shore power than you converter is able to handle the load as they are subject to failure like anything else. Put a meter on your battery and run your jacks as a starting point to diagnosis.
It could be something else, but start with the simplest first or if you do not have a meter or prefer not to use one, tie a jump box that is fully charged to your camper battery and see if it makes things better.
Since I work on RVs, I have to deal with motor issues a lot and I always have my jump box fully charged and close at hand when testing in these kinds of situations. 🙂
Steve and Andra
2012 F350 6.2 gasser SRW LB
Fab Fours front and rear in case we run into a rhino
2019 Northstar Laredo SC