TL;DR; i think you will find it fixed if you upgrade to 6.5.4.3, appears to be regression issue in 6.5.4.0
Seems to be a regression issue in 6.5.4.0 until 6.5.4.2, where something got broken (or implemented) at an ACL filter level in the AP, you can see some threads in the forum about ADP breaking for static IP APs after 6.5.4.0, fixed in 6.5.4.3.
the 6.5.4.3 release notes includes mention of your case of RTLS also dot1x and the static IP issue.
There's a couple of AP datapath related fixes in 'what's new in 6.5.4.0', I would suspect this may be the culprit, but just speculating :)
159610
Symptom: An AP responded to TCP sessions initiated by random clients with source port 80. Modifications in the access control entries fixed this issue.
Scenario: This issue occurred only when a TCP session was initiated from a client from source port 80. This issue was not limited to any specific AP platform or ArubaOS release version.