Inserted characters and deleted characters are still a feature with the zBitx when loaded with the latest, greatest and most-updatest firmware (2 April).
Firmware: v3.051 and v1.06
If you don't know CW, you probably won't see/hear the problems in the video below. If you do, you will.
It is impossible to have a QSO on CW with the zBitx when using the internal keyer in either iambic mode (Update: Or even with a straight key or external keyer).
Compounding the problem - but not shown here due to being on a dummy load - is the lengthy return-to-receive time...about a full second, regardless of the T/R delay dialed in.
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UPDATE (3 Apr):
Several people asked how the zBitx operates in straight key mode with (and w/o) an external keyer.