Arduino IDE: Unpredictable Errors while Uploading Sketches

[glydrfreak]

These errors have been happening to me a lot lately with the Adafruit Bluefruit Feather M0:

First it gets stuck at this stage for way longer than usual--

Then pressing reset (either once or twice) gets me to here--

A less frequent, but still annoying error (separate from the above error)--

I have a feeling it's not just a problem with the Arduino IDE because I've tried to upload via Visual Studio and I've had no luck. (I've also never successfully uploaded via Visual Studio before either. I only tried Visual Studio to see if it was a problem with the Arduino IDE.)

[glydrfreak]

I've now tried to upload the "blink" sketch to the feather M0 via Visual Studio. It worked fine.

... I'll just be commenting my findings as I find them I guess...

[glydrfreak]

I've finally been able to upload my PROTOTYPE4 Sketch via Visual Studio. The above errors that I have explained have come and gone repeatedly, and I find no pattern in what causes such errors.

When do the errors occur?

TOTALLY UNPREDICTABLE!
Some days seem flawless, while other days I can't make any progress with my code at all!

[glydrfreak]

...
Sketch uses 75232 bytes (28%) of program storage space. Maximum is 262144 bytes.
Forcing reset using 1200bps open/close on port COM10
(Upload sequence is stuck after this line prints in the verbose output.)

• I usually get one successful upload with my PROTOTYPE4 sketch after running the "blink" sketch prior. then it repeatedly gets stuck on this line if I try to upload my PROTOTYPE4 sketch again.

• I cannot reproduce the same error with the "blink" sketch.

See Simplified Issue: #7