A person added an extra application link but I do not know more details than that. So I am assuming they added a link incorrectly.
I do not know where the application links are stored to try manually edit them/delete the offending item. Any help would be greatly welcome!
The start of the error in the log is:
2020-03-24 15:25:45,509 ERROR [https-jsse-nio-443-exec-147] "GET /rest/applinks/3.0/applinks HTTP/1.1" c.a.p.r.c.e.j.ThrowableExceptionMapper Uncaught exception thrown by REST service: null
java.lang.NullPointerException: null
at com.google.common.base.Preconditions.checkNotNull(Preconditions.java:210)
at com.google.common.cache.LocalCache.get(LocalCache.java:3936)
This is on a windows server.