Cannot Downgrade Yealink SIP-T43U firmware

[YeaVictor]

Hi,
I am setting up a T46U and T43U on a 3CX system. 3CX system up to date, hosted on premises.
The firmware on the phones were later than the firmware recommended by 3CX.
3CX recommends 108.84.0.100 firmware.
Phones came with 108.85.0.15 firmware.
I was able to downgrade the SIP-T46U to the proper 108.84.0.100 firmware.
However the SIP-T43U did not downgrade, stayed on newer 108.85.0.15 firmware.

Factory reset and tested on network and tested on network with only phone and PC. When attempting the upgrade, I receive the error:

Firmware Update Failed
Software Limit

Any suggestions or ideas.
Thank you.

[YeaVictor]

Follow up.

This is no longer an issue.
3CX now has 108.85.0.15 as its supported firmware.

Thanks!