Me too! I could narrow this down to AX mode in 2,4g. Switching to N-Mode for 2,4g fixed this issue more ore less. I observed strong delay around 1000 to 2000ms from time to time. This mostly but not totally disaapered, once switched to N-Mode or rebooted the device.
I'm curious if this fits to your issue?
I am not sure if this is really AX related, therefor I'll try to setup SQM QoS to make sure I'm not affected by buffer bloat issues. Unfortunately, there is an issue with the current snapshot. So I cannot install the package at the moment.
By the way:
Did you realize that the disk space is limited to around 5,3MiB but temp space to 120MiB. Any chance to increasing some more to the disk?
Cheers