There were error(s) loading the rules: /tmp/rules.debug:52: cannot define table pfB_Top_v4: Cannot allocate memory
I am getting this issue after updating to 2.4.5, however my current setting (as well as the indicated default) for Firewall Maximum Table Entries is 9,000,000
Would decreasing this to 2,000,000 (as indicated in the referenced post)help?
Should I maybe consider increasing it? 18,000,0000
On 2.4.5 that is not indicative of the size of your tables. If it was, it would have a different error that says there are too many entries. This error on 2.4.5 means that it didn't have enough memory at that moment to load the table. Generally it's non-fatal, however, as a later filter reload will likely succeed.
Check the table in question and see if it contains the values you expect. If it does, there isn't likely much to worry about.
This can happen on systems with low RAM or many packages running which consume memory (especially kernel memory).
It should be better on 2.4.5-p1, though that particular scenario is more difficult to isolate and test.