Although I still see the weird dmsg errors, I found the culprit... I removed "irqpoll" from the linux boot parameters:
irqfixup [HW] When an interrupt is not handled search all handlers for it. Intended to get systems with badly broken firmware running.
irqpoll [HW] When an interrupt is not handled search all handlers for it. Also check all handlers each timer interrupt. Intended to get systems with badly broken firmware running.
I have no idea why it was affecting, it's supposed to help, rather than affect... I've always used it (since I found issues with mintbox 2 and another HP elitebook laptop), and had worked fine till now... Thanks ! -- Javier [1] https://www.kernel.org/doc/html/v5.2/admin-guide/kernel-parameters.html