Failed ajax request or invalid json returned (in galley)

Hi @ajnyga @asmecher
I got this error report. Hope it explains the problem

[Sat Jan 05 16:54:14.112102 2019] [cgi:error] [pid 6925] [client 114.125.76.171:43854] AH01215: PHP Warning:  file_put_contents(/home/k2542002/public_html/cache/fc-pluginSettings-1-oldgreggthemeplugin.php): failed to open stream: Permission denied in /home/k2542002/public_html/lib/pkp/classes/cache/FileCache.inc.php on line 90: /usr/local/cpanel/cgi-sys/ea-php56
[Sat Jan 05 16:54:14.110697 2019] [cgi:error] [pid 6925] [client 114.125.76.171:43854] AH01215: PHP Strict Standards:  Only variables should be assigned by reference in /home/k2542002/public_html/pages/index/IndexHandler.inc.php on line 68: /usr/local/cpanel/cgi-sys/ea-php56
[Sat Jan 05 16:54:14.048651 2019] [cgi:error] [pid 6925] [client 114.125.76.171:43854] AH01215: PHP Strict Standards:  Declaration of CustomBlockPlugin::getEnabled() should be compatible with BlockPlugin::getEnabled($contextId = NULL) in /home/k2542002/public_html/plugins/generic/customBlockManager/CustomBlockPlugin.inc.php on line 134: /usr/local/cpanel/cgi-sys/ea-php56
[Sat Jan 05 16:54:14.048405 2019] [cgi:error] [pid 6925] [client 114.125.76.171:43854] AH01215: PHP Strict Standards:  Declaration of CustomBlockPlugin::getBlockContext() should be compatible with BlockPlugin::getBlockContext($contextId = NULL) in /home/k2542002/public_html/plugins/generic/customBlockManager/CustomBlockPlugin.inc.php on line 134: /usr/local/cpanel/cgi-sys/ea-php56
[Sat Jan 05 16:54:14.023515 2019] [cgi:error] [pid 6925] [client 114.125.76.171:43854] AH01215: PHP Warning:  file_put_contents(/home/k2542002/public_html/cache/fc-pluginSettings-1-jatsparserplugin.php): failed to open stream: Permission denied in /home/k2542002/public_html/lib/pkp/classes/cache/FileCache.inc.php on line 90: /usr/local/cpanel/cgi-sys/ea-php56
[Sat Jan 05 16:54:14.001026 2019] [cgi:error] [pid 6925] [client 114.125.76.171:43854] AH01215: PHP Strict Standards:  Declaration of DRIVERDAO::setOAI() should be compatible with PKPOAIDAO::setOAI($oai) in /home/k2542002/public_html/plugins/generic/driver/DRIVERDAO.inc.php on line 19: /usr/local/cpanel/cgi-sys/ea-php56
[Sat Jan 05 16:54:13.986297 2019] [cgi:error] [pid 6925] [client 114.125.76.171:43854] AH01215: PHP Strict Standards:  Declaration of PKPUsageEventPlugin::getEnabled() should be compatible with LazyLoadPlugin::getEnabled($contextId = NULL) in /home/k2542002/public_html/lib/pkp/plugins/generic/usageEvent/PKPUsageEventPlugin.inc.php on line 386: /usr/local/cpanel/cgi-sys/ea-php56
[Sat Jan 05 16:53:50.829606 2019] [cgi:error] [pid 6989] [client 114.125.76.171:43871] AH01215: PHP Fatal error:  Call to a member function getFileId() on null in /home/k2542002/public_html/lib/pkp/classes/submission/PKPSubmissionFileDAO.inc.php on line 1065: /usr/local/cpanel/cgi-sys/ea-php56, referer: https://jurnalbeta.ac.id/index.php/betaJTM/workflow/index/223/5

Please, any thought for the error logs?
I think I have the same error logs here Add galley http error
Still the permission issue.