Hello,
It is highly possible that this is the problem. Every time they define a function in a loop they are creating a new function and creating that app lab warning message. Its not a question of how many times they will be executed, but how many times they will be created. @jdonwells is right that your student is likely exceeding the number of warnings in the loop and thus any other warnings/errors are being ignored or suppressed.
Beyond sharing the suppressed warning issue fact with the student though, I would let this go - this is the time for your student to solve his/her own problems! The issue of the warnings is about the programming language and I would be fine sharing that with the kids. Remixing a students work, identifying where the issue is, and sharing that issue (or sharing the fix) is sharing information about the student code and would cross the ‘CollegeBoard line’. It’s tough to see them struggle, but I personally would not feel comfortable sharing.