Sometimes inputMethodHints do not work at all, or at least that is how it looks like. Setting imhNoPredictiveText for example does not disable predictive text input. It is especially a problem when input mask it used. For example in this case:
When typed to the text field, the text is underlined which is why I am guessing it is the inputMehtodHints not working. Predictive text still seems enabled despite the setting and as the result, the mask as a text remains in the field while something else is typed there.
This occurs on some Android 10 and 11 devices (OnePlus 7, Galaxy Tab S4) and also it has been reportedly reproduced in Android 11 AVD, although I cannot reproduce there myself.