Flexconnect aps losing Controller Associated Time, but still with uptime

Hello, I have some aps, that are losing the association time, they use wan link to communicate with the controller.Looking in the internet I found that the latency should be less the 300 ms, I activated link latency in one access point for test, but looking in the results they are ok:

https://ibb.co/jrMV1RX

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pr 16 13:06:57 kernel: [*04/16/2021 13:06:57.0000] CAPWAP State: DTLS Setup

Apr 16 13:07:54 kernel: [*04/16/2021 13:07:54.0099] dtls_disconnect: ERROR shutting down dtls connection ...

Apr 16 13:07:54 kernel: [*04/16/2021 13:07:54.0099]

Apr 16 13:07:54 kernel: [*04/16/2021 13:07:54.0099]

Apr 16 13:07:54 kernel: [*04/16/2021 13:07:54.0099] CAPWAP State: DTLS Teardown

Apr 16 13:06:57 kernel: [*04/16/2021 13:06:57.0000]

Apr 16 13:06:57 kernel: [*04/16/2021 13:06:57.0000] CAPWAP State: DTLS Setup

Apr 16 13:06:57 kernel: [*04/16/2021 13:06:57.0899]

Apr 16 13:06:57 kernel: [*04/16/2021 13:06:57.0899] CAPWAP State: Join

Apr 16 13:06:57 kernel: [*04/16/2021 13:06:57.0999] Sending Join request to 10.104.240.52 through port 5256

Apr 16 13:06:57 kernel: [*04/16/2021 13:06:57.1299] Join Response from 10.104.240.52

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My aps are : 1815, with ios: 8.5.151.0

Any idea what should I test, or try ? thanks a loot.