Duplicate bugs have occurred in text fields such as command blocks, structure blocks, chat fields, and book and quill. This bug occurs with a high probability, but it will definitely occur if you perform the Steps to reproduce.

Steps to reproduce

1. Enter the syntax in the command block.
2. Change the number of "delay in ticks:"
3. Close the command block settings.
4. Open the command block again.

Observed Results
Duplicate when manipulating text fields.

Postscript
This bug also occurred when operating hover note of the command block. Probably, this bug occurs when you enter it in the input field on the left side of the operation screen such as command block or structure block.

Evidence video

Evidence video.mp4