dfu.py upload fails randomly

Verification

• I searched for similar bug reports and found none was relevant.

What happened?

When running dfu.py, at some point through the uploading process, I almost always recieve an error such as Exception at line 159: not enough values to unpack (expected 3, got 2) or Exception at line 159: 'NoneType' object is not subscriptable

What should happen instead?

I was expecting the upload to succeed without an error

Reproduction steps

I built InfiniTime with the enable DFU flag. I then ran

sudo ./dfu.py -z /path/to/compiled-dfu.zip -a [mac] --legacy

which failed at a random time during the upload with this error

Exception at line 159: 'NoneType' object is not subscriptable

or this error

Exception at line 159: not enough values to unpack (expected 3, got 2)

More details?

It appears that the first error is coming from this line (160) in ble_legacy_dfu_controller.py

(proc, res, pkts) = self._wait_and_parse_notify()

I do not know where the second error comes from, but the error is printed on this line (167) in dfu.py

print("Exception at line {}: {}".format(sys.exc_info()[2].tb_lineno, e))

Edit: It uploaded once (out of the about seven times I tried)

Version

develop with a slight change of a string ('+' -> '^' in timer.cpp)

Companion app

No response