I had something similar, you are not alone! :E
Using my TT for a portable hotel working out of town, I was set up on the grass at a customers property in Powell River BC for about a week and a half.
A few days in the ants invaded me. Took me a few days to figure out they were coming in via my shore power cable.
And I am very fussy about cleaning up all evidence of food too. They went after my rubbermaid garbage container under the sink.
I heavily dusted the wheels and shore power cable area with Comet. They don't like powder on their feet. I sprayed and much more.
I thought I had got them, but over the next 2 years they got worse and worse. They multiplied and took over.
I finally figured it out. They got into my roof via the bathroom Fantastic Fan and built a nest in there. After 2 years of trying everything I could think of I was ready to set fire to it! There was zero food or water source when the TT was stored but they still thrived.
Those useless little round tin bait things do not work. I had them everywhere.
The final solution that eradicated them was liquid Terro. The little $&!?##!'s had a steady run up the wall by the tub and into the ceiling. I put out 2 water bottle lids with a few drops of the Terro in them. One was on the edge of the tub. They loved that stuff. I refilled it multiple times over the course of a week or so.
The most difficult thing was just letting them be, and resisting the urge to attack them with spray. They started coming out of the roof vent and crawling on the ceiling. They acted like they were drunk. Wobbling around, unable to hold on, and they would fall off and die.
2 blinkin years of fighting them! I used a small shop vac to clean up hundreds of them every day for 4-5 days before their numbers dwindled down to nothing.
So yeah, I second the thought, keep your RV clean of food sources!
2007 GMC 3500 dually ext. cab 4X4 LBZ Dmax/Allison - 2007 Pacific Coachworks Tango 306RLSS
RV Rebuild Website - Site launched Aug 22, 2021 - www.rv-rebuild.com