v3.8.11 on Debian9 with mariadb 10.1 cannot login?

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Hello,

I am trying to do some research for a friend to upgrade their forum instance. They are currently running a fully patched debian 8 system with vB 3.8.11 and everything works properly.

In order to try to help them with the upgrade process I have made a VM clone of that system. If I uninstall php 5.6 from debian 8 and install php 7.0 there are no issues and their forum works properly inside the virtual machine.

However, if I do a full apt-get upgrade; apt-get dist-upgrade to debian 9 then when I try to access the forum index page I get the message

'You have been banned for the following reason: No reason was specified. Date the ban will be lifted: Never'

If I try to access the admin page after I enter the login credentials it simply loops back to the login page.

My suspicion is that something in MariaDB 10.1 for Debian 9 has changed, maybe some system setting, and it is causing some query to behave badly.

I have tried removing ever plugin that was installed to vB and also ensured all of the php files are untouched.

I have turned on vB debug information but I don't see anything obvious.

I can tell that on debian8 with php 5.6 or php 7.0 when it works more queries are being executed when hitting the login page.

Has anyone else seen a similar issue or have any suggestions on what I could try to track down the source of the problem?

Thanks in advance for reading and any suggestions.