Android Camera Issues

We have a scenario we just can't figure out, technically or logically. I'll try to give as much info as possible in hopes someone has an idea on how to resolve or troubleshoot.

- 2 types of Android devices, Lenovo M10 tablets (various generations) and Blackview rugged phones (BV4900s & BV5900)
- Enrolled into Intune using QR code as Corporate Owned Dedicated Devices
- Running in kiosk mode with managed home screen
- Camera settings set to "Not Configured"

Blackview devices used mainly for 1 in-house developed app for taking photos of goods-in/out
Blackview devices have worked flawlessly for 18 months+ with no intervention. Camera app was never re-added after enrollment.
Some Blackview devices have now started to "lose" the camera functionality. Enrolling / re-enrolling / manually pushing the system camera (com.mediatek.camera) or an open source camera (Open Camera) fixes things some times, not others. Re-enrolling the same device multiple times without changing anything sometimes gets the camera working again.
(We realise these devices aren't on the officially supported Android Enterprise list, but they used to work fine)

Lenovo devices used mainly for Barcode scanning through an internally developed PowerApp.
Lenovo (Gen-1) devices, system camera stripped as part of enrollment (as expected) and pushed back out as Android Enterprise system app (org.codeaurora.cam) - Working 100% of the time (so far)
Lenovo (Gen-2 & 3) devices, system camera stripped as part of enrollment (as expected) and pushed back out as Android Enterprise system app (com.mediatek.camera) - Working ~50% of the time (the camera is always there, the barcode scanning funtionality doesn't always work). Enrolling / re-enrolling / manually pushing the system camera or an open source camera fixes things some times, not others. Re-enrolling the same device multiple times sometimes gets the barcode scanning working again.

We have tried
- Editing the QR code so system apps aren't removed
- Pushing the system camera app as an Android Enterprise system app
- Pushing an open source (Open Camera) camera app
- Removing the devices from Intune entirely (everything works when we do this)

From the above, the only conclusion we can draw, with admittedly limited data, is it seems to be related to the system camera app being com.mediatek.camera. Other devices with different chipsets don't seem to display this behaviour. What we don't understand is how this can work intermittently and what could have been updated that would cause previously working devices to start to lose the camera. The Intune config hasn't been touched.

Microsoft have told us this is a device issue and closed the support case, yet this behaviour only happens when you enroll in Intune. I've not been able to find any meaningful support avenues for MediaTek.

If anyone has any ideas, I'd really appreciate. We'd like to continue using Intune for management, but unless we can get this resolved, we're going to have to look elsewhere.