Haven’t they had similar problems in the past with other aircraft such as the F-22?
Yes. There was a problem in the F-22’s OBOGS system. I believe a faulty valve was the culprit as has been fixed. It would seem to me the T-45 problem is age-related, perhaps mold or some other contamination in the oxygen system that will require line replacement.
There might have been. However, this might be an ‘age’ problem. Thirty-five years in service is a long time, and maybe some of the oxygen lines might have leaks to allow contaminants in.