Netgear dgn3500 wireless -> eth0 dmesg error

I have an old router (Netgear Dgn3500) that has errors displayed in dmesg and / or logread (only when there is traffic from wireless to wan interface):

kern.err kernel: ltq_etop 1e180000.etop eth0: tx ring full

logread | grep "tx ring full" | wc -l

uptime 17:34:27 up 1 day,  6:20,  load average: 0.04, 0.01, 0.00

Openwrt version: OpenWrt 19.07.5

I would like to understand what they are due to as I do not seem to require anything exceptional from the router in question.

I know that it is an obsolete product and that there are various alternatives on the market but I would like to try to understand the errors

thanks to anyone who wants to answer me

if you are interested I have partially solved it by installing and configuring "sqm"

the number of dmesg errors has decreased there are still some "random errors" that cannot be removed because as I have specified the router is obsolete