I am using multiple webvisu containing XY charts, histograms, texts and various widgets. Multiple users and clients (laptops, mobile phones) access the webserver on the PLC (Beaglebone black). It works pretty well but every so often I get a crash of the webserver.

Example 1:
1520322979, 0x00000071, 1, 0, 0, File <file>$PlcLogic$/$visu$/element-meter-meter90-gray-topright.svg</file> requested ...
1520322979, 0x00000071, 1, 304, 0, State: Not Modified
1520322981, 0x00000071, 8, 81, 0, EXCEPTION <task>WebServerTask</task> <ip>0xb6e08ad2</ip> <bp>0xb6000040</bp> <sp>0xb5fdec28</sp>
1520323014, 0x0000100c, 1, 0, 0, VisuFctCheckForUnusedClients: Removing Client at Address: 3061861096
1520323014, 0x0000100c, 1, 0, 0, VisuFctCheckForUnusedClients: Successfully Removed Client at Address: 3061861096, IEC-ID was: 0

Example 2:
1519890714, 0x00000071, 8, 81, 0, EXCEPTION <task>WebServerTask</task> <ip>0xb6d8dad2</ip> <bp>0xb5f00040</bp> <sp>0xb6191c28</sp>
1519890721, 0x0000100c, 1, 0, 0, VisuFctCheckForUnusedClients: Removing Client at Address: 3048407776
1519890721, 0x0000100c, 1, 0, 0, VisuFctCheckForUnusedClients: Successfully Removed Client at Address: 3048407776, IEC-ID was: 4
1519890731, 0x0000100c, 1, 0, 0, VisuFctCheckForUnusedClients: Removing Client at Address: 3048524848
1519890751, 0x0000100c, 2, 0, 0, VisuElemXYChart: Not enough space for handling creating/destroying clients

Example 3:
1518682903, 0x00000071, 1, 0, 0, State: successful
1518682918, 0x0000100c, 1, 0, 0, Visu_PRG: Creating Client for Extern-ID: 968082
1518682918, 0x0000100c, 1, 0, 0, Visu_PRG: Creating Client successful for Extern-ID: 968082 Returned IEC-ID: 5
1518682934, 0x00000071, 8, 81, 0, EXCEPTION <task>WebServerTask</task> <ip>0xb6df0ad2</ip> <bp>0xb6e897d4</bp> <sp>0xb697ec28</sp>

Example 4:
SyncSendService failed
TlsCreateContext: Creating the TLS context for namespace 'Webserver' failed
TlsCreateContext: Failed to read certificate ./PKI/cert/server.cer in namespace WebServer

debian@beaglebone:~$ uname -a
Linux beaglebone 4.9.78-ti-r94 #1 SMP PREEMPT Fri Jan 26 21:26:24 UTC 2018 armv7l GNU/Linux

debian@beaglebone:~$ cat /etc/issue
Debian GNU/Linux 9 \n \l

BeagleBoard.org Debian Image 2018-01-28

Do you have any ideas of the possible causes of these multiples crashes?
Thanks,
Anthony