Hi Frank,

There isn't nearly enough information provided for us to do anything:

1) Is this a new problem?
2) Does this happen with every single test case (if you just open a new document and insert a single footnote and then delete it, do you see a crash?)
3) Can you attach a document (simpler the better) that crashes for you when you delete a footnote?

Marking as NEEDINFO - once you provide adequate information please set to UNCONFIRMED. Thanks

In addition to what Joel indicated, could you upgrade to last stable LO version 5.1.5, rename your LO directory profile (see https://wiki.documentfoundation.org/UserProfile#Mac_OS_X) and give a new try?

No repro on 

Version: 5.2.0.4
Build ID: 066b007f5ebcc236395c7d282ba488bca6720265
CPU Threads: 2; OS Version: Mac OS X 10.11.6; UI Render: default; 
Locale: en-GB (fr.UTF-8)

with enclosed testfile.

1) Open testfile.
2) Put cursor after footnote indicator "a"
3) Press backspace key to delete footnote
4) Footnote is deleted correctly and remaining footnotes renumbered.

No crash.

Created attachment 127093 [details]
Test ODT with footnotes

No reproduction anymore on 5.1.5.2 release

Problem resolved

Thank you!

(In reply to Frank Jerusalem from comment #5)
> No reproduction anymore on 5.1.5.2 release
> 
> Problem resolved
> 
> Thank you!

Just nitpicking, version field corresponds to the oldest version where the bug can be encountered.