Authors cant complete submission of their articles

hi i have posted this before but up till this time I didn’t get any good response, it happens that i am getting complaints from authors who were trying to submit their articles on our journal system, we run an online version of the OJS, at first I thought its the network of where they were, but I decided to give it a trial and I discover that when they to the stage three of the submission process after entering all necessary information like keywords e.t.c. and click on save to continue it get stuck and won’t eventually submit, please anyone who can help solve this issue: below is the error log:

[15-Dec-2022 19:46:20 Africa/Lagos] PHP Fatal error: Uncaught Error: Call to a member function getFullName() on null in /home/wnjmscom/public_html/journal/lib/pkp/classes/submission/reviewAssignment/
Stack trace:
#0 /home/wnjmscom/public_html/journal/lib/pkp/classes/submission/reviewAssignment/ ReviewAssignmentDAO->_fromRow(Array)
#1 /home/wnjmscom/public_html/journal/lib/pkp/classes/task/ ReviewAssignmentDAO->getIncompleteReviewAssignments()
#2 /home/wnjmscom/public_html/journal/lib/pkp/classes/scheduledTask/ ReviewReminder->executeActions()
#3 /home/wnjmscom/public_html/journal/lib/pkp/plugins/generic/acron/ ScheduledTask->execute()
#4 [internal function]: PKPAcronPlugin->shutdownFunction()
#5 {main}
thrown in /home/wnjmscom/public_html/journal/lib/pkp/classes/submission/reviewAssignment/ on line 453

Hi @Amolowe2021,

Please do not post multiple times on the same issue. You have already posted here: Authors having issue completing submission process - #7 by Amolowe2021

This goes against our guidelines for appropriate forum behavior: Forum Guidelines and Code of Conduct

PKP Team