I tried it again, twice, at default EGCC Gate 8, starting directly with the catering, and I had two cases:
- Once, two minivan came, and went away without any problems.
- The 2nd time, a catering truck came in the back, and a minivan came in front, and even in this case they went away normally and I was able to call the pushback.
The difference is due to slightly changes in airplane height due to loading and inertia, because the rear door height is just about around the decision threshold between a minivan and a catering truck, but it worked in both cases.
Are you using a custom config for the airplane ? Try to Reset it to default.