What could be the cause?
Unit below shows all points removed on March 31st.
It falls in line with me upgrading the motherboard, and reducing the GPUs from 2 to 1.

https://www.boincstats.com/stats/-5/host/detail/367138705/charts

Forget BOINCStats, what does it say for that computer, on your Account page, for the relevant projects?

Have you checked that you have allowed relevant projects to export stats? Someone else posted more of less the same question a few days ago.

Yes, as much as possible, I try to receive stats.
World Community Grid doesn't seem to upload, but most of the rest of the projects seem to do.
Most of the points are Collatz, which seem to not reflect this shift.
in fact, the Collatz only show points accumulated after this point reduction (Mar 31st) on that host.
My user stats don't seem to reflect this sharp reduction though; I would have noticed it!

https://www.boincstats.com/stats/-5/user/detail/76980179455/charts

Why do I lose credit in BOINC combined stats?

When you attach to a new project, or reattach to a projects that restarts after a 'break' your CPID for a project can change. It takes a while for all projects to line up again. During this time, you may loose some credit in the combined stats, and sometime all credit will go to a new account with a new CPID.

https://www.boincstats.com/page/faq

BOINCStats is a third party website, it has nothing to do with BOINC. Therefore any problems you have with it, please take it up on their own forums: https://www.boincstats.com/forum/

The only authoritative credit stat is the one on the website of the project awarding the credit.

Everything else is secondary and derivative. Check it out at the source first.

What could be the cause?
Unit below shows all points removed on March 31st.
It falls in line with me upgrading the motherboard, and reducing the GPUs from 2 to 1.

https://www.boincstats.com/stats/-5/host/detail/367138705/charts

I wondered where 140M credits disappeared from my host's BoincStats account. This is Willy's reply.

Yes, after 60 days of inactivity a host is ignored.

However, this does not mean that the host credit is missing from your user credit.

What could be the cause?
Unit below shows all points removed on March 31st.
It falls in line with me upgrading the motherboard, and reducing the GPUs from 2 to 1.

https://www.boincstats.com/stats/-5/host/detail/367138705/charts

I wondered where 140M credits disappeared from my host's BoincStats account. This is Willy's reply.

Yes, after 60 days of inactivity a host is ignored.

However, this does not mean that the host credit is missing from your user credit.

Must be a different issue, since mine were discounted 6 days ago.
Rather than 'discounted', it could be that they were just 'transferred' to another host.

Rather than 'discounted', it could be that they were just 'transferred' to another host.

Have you checked the project yet?

It's not impossible that your hardware change (different motherboard, you said) has triggered a new host ID number in the project database. That is a known operation in BOINC server circles - as is the way to recover the old ID number. I know how to do that, but I won't bother to explain until we know whether it's needed or not.