Problem when signing documents for user Lotus Notes

Good afternoon, colleagues, there was a problem when signing documents for a user (manager). Documents are signed with an electronic digital signature. Upon the user's assurance, the documents are signed automatically, without his knowledge. The event logs were checked, logs from remote connections, unauthorized connections were not detected. All passwords in the EDS in Lotus were changed, the operating system was reinstalled anyway, the problem will continue.

Please help with solving the problem, are there any errors, system bugs that affect this process.