That's very likely moisture under the paint. My brown van did this - the painter left it outside his workshop in primer in the rain for 2 weeks before painting it

. It looked perfect for about 4 months, then when I left it out in the hot sun for a week patches just like this appeared, again near seams where water had been trapped. They never spread or got worse in the three years after.
I had done all the work on the van so I was 100% sure there was no rust in these areas, and when I repaired one of them myself, it was just an empty bubble and perfectly clean primer and metal beneath.
Anyway.
Most mobile paint repair people will be able to do a decent enough job of that, providing you know what the exact colour the van is painted in. They'll mix paint to match, but it's never 100% perfect so they'll use their judgement as to where to "lose" the repair - ideally on a swage line or seam. This isn't always possible, so sometimes a fade out of the repaired area needs to be done in the middle of a panel. This isn't ideal and you'll often end up with a bit of a halo appearing round the repair after 6 months to a year, where the thin edge of the faded out lacquer starts to oxidise and weather. You can usually improve this by just buffing it up with some mild cutting compound but it will keep coming back unless they paint the whole panel.
What the mobile repair lads do isn't magic, the materials they use are more or less the same as in a normal bodyshop - but they approach the job from the perspective of providing a reasonable result with the least amount of work by bending the rules and pushing their materials to the limit. A normal bodyshop would (should?) just aim to do a proper job following straightforward industry standard processes which generally means that they'll be painting at least one full panel, something that can't really be done on a mobile basis.
You might find people are reluctant to take this job on because they're also worried it'll be rust underneath. These guys just want straightforward work they can bosh out in a few hours and move on without fear of a quick job escalating into something bigger - they'd rather do 3 or 4 scratched plastic bumper corners on lease return modern cars every day than mess around with old stuff that's already had more work than Madonna! In fact the few guys in the trade that I know will usually refuse to do any "rust" repair, and if they do they will usually make it very clear to the customer that there's absolutely no guarantee of the quality or longevity of the repair - they'll do their best in an allotted time and that's that.