Apache error investigation

[idiocrate]

Greatings,
i'm having trouble figuring the origin of an apache error :
i'm hosting a DokuWiki website and when i try to resize image into the CKGedit's editor the image which is in base64 is converted into another base64 String value, my problem is this new String cause the server to crash and i would like to understand why.

when i access the error_log file i see this lines :

[Tue Jul 03 10:44:53.524559 2018] [core:notice] [pid 17013] AH00052: child pid 18385 exit signal Segmentation fault (11)
[Tue Jul 03 10:44:53.524606 2018] [core:notice] [pid 17013] AH00052: child pid 18386 exit signal Segmentation fault (11)
[Tue Jul 03 10:44:54.526694 2018] [core:notice] [pid 17013] AH00052: child pid 18384 exit signal Segmentation fault (11)
[Tue Jul 03 10:44:54.526749 2018] [core:notice] [pid 17013] AH00052: child pid 18387 exit signal Segmentation fault (11)
[Tue Jul 03 10:44:54.526759 2018] [core:notice] [pid 17013] AH00052: child pid 18390 exit signal Segmentation fault (11)
[Tue Jul 03 10:44:54.526768 2018] [core:notice] [pid 17013] AH00052: child pid 18392 exit signal Segmentation fault (11)
[Tue Jul 03 10:44:54.526777 2018] [core:notice] [pid 17013] AH00052: child pid 18395 exit signal Segmentation fault (11)
[Tue Jul 03 10:44:54.526785 2018] [core:notice] [pid 17013] AH00052: child pid 18396 exit signal Segmentation fault (11)
[Tue Jul 03 10:44:54.526793 2018] [core:notice] [pid 17013] AH00052: child pid 18405 exit signal Segmentation fault (11)
[Tue Jul 03 10:44:54.526876 2018] [core:notice] [pid 17013] AH00052: child pid 18412 exit signal Segmentation fault (11)

could you tell me how to investigate further as i'm noob in the Unix world
best regards