Where are error codes documented?

FAQ
1

Using a Wemos D1 mini I get a lot of errors but have no idea what exactly they mean.
Where are the error codes documented? Waht does error code 19, 15 or 20 mean?

[21294] Cmd error
[21396] Cmd skipped:19
[21498] Cmd skipped:20
[21599] Cmd skipped:19
[21699] Cmd skipped:20
[21799] Cmd skipped:19
[21899] Cmd skipped:20
[21999] Cmd skipped:19
[22099] Cmd skipped:20
[22199] Cmd skipped:19
[22299] Cmd skipped:15
[22800] Cmd skipped:15
[23301] Cmd skipped:15
[23802] Cmd skipped:15
[24303] Cmd skipped:15
[24804] Cmd skipped:15
[25305] Cmd skipped:15
[25806] Cmd skipped:15

2

Here https://github.com/blynkkk/blynk-library/blob/master/src/Blynk/BlynkProtocolDefs.h

However your problem seems related to WI-FI issues.