ZHA Tradfri OTA firmware update fails with size error

I have tried to update Tradfri firmware using the ZHA integration, but I receive the same error mentioned here. https://github.com/home-assistant/core/issues/42261 It says to use beta firmwares, and that these supposedly have correct sizes, but I have verified that ZHA does indeed download the beta firmware, however, it still fails with a size mismatch, generating this warning entry in the log:

2020-11-11 11:26:08 WARNING (MainThread) [zigpy.ota.validators] Image OTAImageHeader(upgrade_file_id=200208670, header_version=256, header_length=56, field_control=<FieldControl.0: 0>, manufacturer_id=4476, image_type=16900, file_version=537040419, stack_version=2, header_string='GBL GBL_tradfri_sy5882_bulb_ws', image_size=208242) is invalid: Image size (208180) must be a multiple of 64 bytes

What am I doing wrong?

Hmm, strange.

Did you download the firmware to the OTA directory? OR did you add the beta URL to the config?
I added the URL and it seems to work fine for me.

Hey. I tried both things, and I get the same mismatch error regardless, and it reports the same size, so I seem to be getting the same file. Would it have anything to do with the current firmware installed on the device, or is the error caused simply by Zigpy not liking the size of the file at hand?

I am having the same issue. I am using ZHA with Deconz II on HA 0.117.6.
I fixed it by downloading firmwares, instead of using the beta URL: https://github.com/home-assistant/core/issues/42261#issuecomment-715393719