Failure querying DNS through UDP on specific server

I’m using the acme script to issue HTTPS certificates on my servers. One of my server (let’s call it server A) fails to finish the acme cert issuing process. I have tried ~5 times, they all fail with timeout error while trying to query earl.ns.cloudflare.com (which is my base domain’s nameserver). I also face timeout error on server A while using dig google.com @earl.ns.cloudflare.com on that server (other servers and my local machine are all fine). But on server A, I can successfully query 1.1.1.1. If I append a +tcp to the dig command, it also succeeds on server A.

What would be the root cause here?

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