Check with McD to see if they changed anything in the refinishing process in the last 60-90 days. For example, if they changed suppliers of a given chemical without making adjustments to each of the other components making up the refinishing process, there could be issues.
Don't need to be adversarial when you contact them - heck, you might be doing them a favor if you're the first to report the issue & work with them to correct it.
Side note: When I was in manufacturing, we discovered that one plant had a significant jump in certain defects two weeks each year. This was happening for years and years. Consultants came in, paid big $$, they couldn't figure it out. I visited the plant, met with the people & determined that the senior employees took vacation the first week of deer and small game season. Once we knew that, we were able to put processes in place that corrected the issue forever.
Hope this helps