Symbol Editor corrupts Filestructure

Symbol Editor in KiCad Version 8 rc1 & rc2

Loading Symbols from KiCad 7.0.10 works fine, but after editing one symbol successfully and saving it, the file is corrupted. The next time you start the Symbol Editor you get the error message:

Errors loading symbols: Error loading symbol library xxx

Un-terminated delimited string in "filedir\xxx.kicad_sym", line 6801, offset 36.

The file content in my specific example looks like this:

File xxx.kicad_sym is correct and working:

   (property "Datasheet" "D:\\OneDrive\\Elektronik\\Marani Parts\\Diodes\\ESD\\2105241942_TECH-PUBLIC-TPD4E001DCKR-TP_C2827639.pdf" (at 21.59 0 0)
      (effects (font (size 1.27 1.27)) (justify left) (hide yes))

After editing any symbol with symbol editor:

   (property "Datasheet" "D:\\OneDrive\\Elektronik\\Marani
					Parts\\Diodes\\ESD\\2105241942_TECH-PUBLIC-TPD4E001DCKR-TP_C2827639.pdf" (at 21.59 0 0)
      (effects (font (size 1.27 1.27)) (justify left) (hide yes))
    )

Steps to reproduce

1. Start KiCad
2. Start Symbol Editor
3. Change one existing Symbol
4. Save the Symbol
5. Close Symbol Editor

KiCad Version

Application: KiCad x64 on x64

Version: 8.0.0-rc2-133-g7f5433f0f2, release build

Libraries:
	wxWidgets 3.2.4
	FreeType 2.12.1
	HarfBuzz 8.3.0
	FontConfig 2.14.2
	libcurl/8.5.0-DEV Schannel zlib/1.3

Platform: Windows 11 (build 22631), 64-bit edition, 64 bit, Little endian, wxMSW

Build Info:
	Date: Jan 26 2024 06:18:13
	wxWidgets: 3.2.4 (wchar_t,wx containers)
	Boost: 1.83.0
	OCC: 7.7.1
	Curl: 8.5.0-DEV
	ngspice: 42
	Compiler: Visual C++ 1936 without C++ ABI

Build settings: