This is the first time I’ve noticed this:
When inputting MX records or SRV records, when I input “0” for SRV and start to make a new record, the “0” I’ve entered previously can’t be used again when making the new record (although I intentionally just left it 0 as the last record since I want to put 0). Same happens for MX record. When I inputted “20” as the priority and made a record. As I started to make another record and tried to submit it while leaving the “20” that was previously there un-touched, I had to re-type the 20 to get it to work.