Tried to play with $ROOTSYS/tutorials/tree/tree1.C sample. Loaded it in Cling first:
root  .x tree1.C
(TTreeViewer *) 0x55cc8190bb80
File name : tree1.root
Everything is going well so far, the browser and tree viewer are there both. But clicking on 'px' leaf just crashes ROOT:
root  *** stack smashing detected ***: <unknown> terminated
I also tried to reproduce that in v6.10/08 version, but it didn't crash there.
UPD Tried to reproduce on macOS also in ROOT 6.18/04 (built by clang-1001.0.46.4), and it also crashed, but after clicking on 'pz' leaf instead, with this log:
root  root.exe(62631,0x113d925c0) malloc: *** error for object 0x408387980062c6b0: pointer being freed was not allocated
root.exe(62631,0x113d925c0) malloc: *** set a breakpoint in malloc_error_break to debug
Hope this helps.