I've fixed several mice at upstream Linux kernel with HID_QUIRK_ALWAYS_POLL (0x00000400) already.

So please let me know if your mouse disconnects every x seconds or every minute when no user-space driver is running and nothing polls the mouse this way (usually on a virtual terminal [VT] without gpm running).

Please test if the kernel boot option

usbhid.quirks=0xaaaa:0xbbbb:0x00000400

fixes the issue while aaaa is the USB vendor ID and bbbb is the USB product ID in hex from lsusb or lsusb -vvv output.

If this fixes your issue, please let me know the USB IDs, your mouse model, which distro you use and if you need it for kernel < 4.16.

Thanks in advance!