These intermittent fuse blows can be maddening to find. In a fiberglass body RV the most likely fault places are where hot wires and grounded metal come (chafe) together, and where hot and grounded wire connections are in close proximity to each other (where short circuit wiring faults may exist). The 2nd set of places most likely would be in wire interconnection boxes and the light fixtures themselves.
If these fixtures are all incandescent lamps, I would start with changing out ALL of these bulbs, as an easy thing to do in case there is an internally intermittent shorted bulb. This is VERY uncommon, but again, an EASY thing to try.
I troubleshot such an intermittent fuse blowing problem for months that was on my refrigerator 12 volt supply circuit. I finally found the hot wire chafing against the grounded refrigerator base plate. Part of my troubleshooting effort was to wire in a temporary fuseholder and fuse at different locations in the hot wiring to try to pin down the location of the intermittent short. I would use a temporary fuse with a smaller amperage rating than the main branch fuse so it would blow first. Using this approach and being patient, I learned the location where the short was before and beyond in the wiring; and kept moving the temporary fuse towards the fault using this knowledge. If the main fuse blows, but the temporary (smaller) fuse doesn't, then the temporary fuse is beyond the fault. If the temporary smaller fuse blows, but the main fuse doesn't, then the temporary fuse is before the fault.
Good Luck!!!