[RPI4 - kali64] airmon-ng stops working after a few minutes

Hello, as this is my first post sorry if I posted in a wrong section or something. I'll get used to it soon enough.
Anyway I ask for some hints in order to troubleshoot an issue I have on my Raspberry pi 4 + kali 64 latest stable build + 5.1v adapter from the original kit: I can successfully put my internal wifi adapter in monitor mode and I do indeed receive traffic data with airodump-ng, yay!
But after a couple of minutes airmon slowly dies, clients seem to disappear in a matter of minutes one after the other and after a while airodump simply stops working, it simply does not receive anything more unless I reboot the pi and start over (and the issue repeats itself again).
When this happen, it does not matter if I put down and up the wlan0 or wlan0mon, if I start and stop monitor mode, if I "check kill" or stop, start or restart network manager, whenever I user airodump-ng it's very laggy and doesn't detect a single network or a single packet.
Rebooting and restarting seems to temporarily fix, but after a 5/7 minutes it breaks again.

I've been searching for hours but all the posts are rather old: some suggests that kali 64 for pi is still totally wip and isn't reliable, some other suggests to use an external wifi adapter (whereas is stated everywhere that the pi 4 is capable of monitor mode with the onboard wifi chip, and mine does get into monitor mode). Nothing really useful in my scenario.
Does anyone have a clue on what this issue can be? The installation is pretty plain, I didn't plug custom firmwares or scripts from some place which might have broken something.
A peculiar thing I noticed is that if i start airmon-ng without --ignore-negative-one option a message pop up warning about the fixed negative one -1 thing in the right top corner but the outcome (airmon-ng slowly but surely dying over time until reboot) does not change. Adding the flag maybe let airmon live a little bit longer, maybe, but it can just be a wrong perception.

Thanks in advance