As far as I know that is not a requirement. Not yet at least.
A friend of mine still has their nodes misconfigured with regards to UDP, and they did not get disqualified.
@brad-pea Disqualification is usually due to Audit failures. They can be searched with commands such as:
docker logs YOUR_NODE_NAME 2>&1 | grep -E 'GET_AUDIT' | grep 'failed'
(this is for docker logs, the command needs to be changed if your logs are redirected to a file)
If it turns out to be a software bug, the support team may un-disqualify you, but past experience showed that this case is almost non-existant 
When a node gets disqualified, it’s either because it did not replied correctly to audits or stayed offline for too long. Either way, there’s no way back.
I’m sorry 
Now, many SNOs still don’t get why there’s no alert prior to being abruptly disqualified, that is a topic that has been discussed many times in the past, with no obvious consensus yet.
See: