eap_tls: Failed to read from child output

[Burn Zero]

Hi,

Our laptops are using Certificate authentication (EAP-TLS) to connect to
the wifi network. Sometimes, I get the following errors in FreeRADIUS
servers:

Fri Sep 10 10:59:58 2021 : Auth: (185911) Login incorrect (eap_tls: Failed
to read from child output): [machinename] (from client WIFI-WLC port 49315
cli
Fri Sep 10 10:59:59 2021 : Auth: (185947) Login incorrect (eap_tls: Failed
to read from child output): [machinename] (from client WIFI-WLC port 49315
cli
Fri Sep 10 10:59:59 2021 : Auth: (185951) Login incorrect (eap_tls: Failed
to read from child output): [machinename] (from client WIFI-WLC port 49315
cli
Fri Sep 10 10:59:59 2021 : Auth: (185949) Login incorrect (eap_tls: Failed
to read from child output): [machinename] (from client WIFI-WLC port 49315
cli
Fri Sep 10 10:59:59 2021 : Auth: (185986) Login incorrect (eap_tls: Failed
to read from child output): [machinename] (from client WIFI-WLC port 49315
cli

It is very random and also we are not able to reproduce the issue. I have
searched on the internet and freeradius mailing list archives and I don't
see such issues discussed before.

Could you please help on how to move forward?

Thank you.