I owned two Winnebago motorhomes and think they were decent coaches. However, I also believe their method of attaching the roof edge in that metal channel is a poor design. Relying on some caulk to keep it in place is IMO just stupid. That said, I would not reject an otherwise properly maintained Winnebago coach.
I used 2" Eternabond tape along that seam and it held up just fine for the 8 years I owned my last Winnebago. If you use a good urethane caulk like 3M 4200/5200 or Geocel ProFlex it should last years.