cannot serialize xmlrpcresp objects whose content is native php values

[Tsokotsa]

I have a mailscanner running with mailwatch on a centralized environment. It is installed on Centos 7.9 with PHP 5.4.16
I have other clients running Mailscanner and everything works ok. However when emails are detected as SPAM, i am unable to view the area to release emails, and when i enable debug below is the error i get:

--GOT---
HTTP/1.1 200 OK
Date: Mon, 12 Jun 2023 06:01:32 GMT
Server: Apache/2.4.53 (CentOS Stream)
X-Powered-By: PHP/8.0.27
X-XSS-Protection: 1; mode=block
X-Frame-Options: SAMEORIGIN
X-Content-Type-Options: nosniff
Expires: Thu, 19 Nov 1981 08:52:00 GMT
Cache-Control: no-store, no-cache, must-revalidate
Pragma: no-cache
Set-Cookie: MW_LANG=en; path=/
Set-Cookie: PHPSESSID=oer0vriljoid6qn1eg6sosnrhq; path=/; HttpOnly
Connection: close
Content-Type: text/html; charset=UTF-8

cannot serialize xmlrpcresp objects whose content is native php values
---END---
HEADER: Date: Mon, 12 Jun 2023 06:01:32 GMT
HEADER: Server: Apache/2.4.53 (CentOS Stream)
HEADER: X-Powered-By: PHP/8.0.27
HEADER: X-XSS-Protection: 1; mode=block
HEADER: X-Frame-Options: SAMEORIGIN
HEADER: X-Content-Type-Options: nosniff
HEADER: Expires: Thu, 19 Nov 1981 08:52:00 GMT
HEADER: Cache-Control: no-store, no-cache, must-revalidate
HEADER: Pragma: no-cache
HEADER: Set-Cookie: PHPSESSID=oer0vriljoid6qn1eg6sosnrhq; path=/; HttpOnly
HEADER: Connection: close
HEADER: Content-Type: text/html; charset=UTF-8
XML error at line 1, check URL
XML-RPC Error: Invalid return payload: enable debugging to examine incoming payload (XML error at line 1, check URL)

==================
on the client side i use Centos Stream 9 and php 8.0.27

i am running postfix on both systems, apache.

I tried changing the xmlrpc version to 1.1 and still i get the same error. the current installed xml is 3.0 BETA.
mailwatch version 1.2.10