RichTextBox Select Will cause the main thread to freeze and memory to continue to increase

### Description

After loading FlowDocument, dragging and selecting some elements with the mouse can cause the program to get stuck.This will not happen if I use the xml formatting tool to format the text and then load it.

### Reproduction Steps

[bug.zip](https://github.com/dotnet/wpf/files/11186990/bug.zip)
This is the testing program
Xaml exports flowdocument to 1. txt ，
1.xml: I use the xml tool to format

### Expected behavior

can freely select

### Actual behavior

Program stuck, memory overflow

https://user-images.githubusercontent.com/20938585/230810785-74935978-5249-4f28-be56-09df47d4a83c.mp4

### Regression?

_No response_

### Known Workarounds

_No response_

### Impact

_No response_

### Configuration

_No response_

### Other information

_No response_