Receive location becomes disabled without any error in logs

Hi,

I'm a newbie in BizTalk.

We have Receive locations that suddenly becomes Disabled without any error in the logs.

In the Core-file Transfer log, we see information about file transfers. No error either.

What these Receive locations have in common: they all transfer .pdf files from a network share to another.

Any idea what could happen and why there's no error anywhere ?

Thanks in advance.

Regards,

Eric