Date field behaves weird when "display" MM/YYYY is used

[mit-stauffer]

Description

When displaying a date field in the panel in the format MM/YYYY, the date input jumps to 08/2025 after saving, no matter what I selected. No other options are used (except width). Tried it in the 4.2 startkit

datetest:
   type: date
   display: MM/YYYY
   width: 1/4

The content .txt files saves the wrong date:
Datetest: 2025-08-01