This is a serious bug in Adobe Acrobat version 24.1+, where the "Add Text" tool attempts to edit existing text in a document. Often, users wish to simply add text to a document, but if the page is crowded (such as an IRS form), the application attempts to edit the closest text around the cursor instead of simply adding additional text to the document.

Previously there was a tool called "Typewriter" which only added text. Adobe removed this tool in favor of the "Add Text" tool, which was a very bad decision IMO.

The intent of the user should be considered before removing a feature. Some users may want the ability to edit text in a PDF, and that's fine. However, wanting to add text vs editing text is completely different - especially when filling out PDFs that were not prepared as forms (like the IRS and state tax boards often do). Having the ability to add text to a document and not edit existing text is a crucial feature.

Workaround:
Use a different PDF editor (non-Adobe). Most have a typewriter feature, thankfully.