Could you provide more details about the devices?
What are the firmware versions they are using?
Do they have remote access enabled or are they accessed via VPN?
What other configurations are made to the device?
Are there any unusual behaviors, such as increased data usage or slower performance?
Would it be possible to get a troubleshoot file from one of the devices? To generate the file, access router's WebUI, go to System -> Administration > Troubleshoot section and download troubleshoot file from there. You can attach it by editing your question.
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