We have a customer with a web shop running Odoo 8. (We're porting to 12 or 13.)

A strange behavior sometimes occurs. Last week, Odoo changed all sales to be from one of the customers! Usually "Administrator" is marked as the sales person. But last week, that was changed to Marie something, the latest customer to perform a purchase!

Quite stressful to sort out, but I believe managed!

During this weekend, an older error occurred. A customer performed a purchase and the Administrator is marked as the customer.

I'll go into the database and change that manually, using PhpPgAdmin, so the purchase will point to the correct customer.

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My question is, how do we prevent this from happening in the future?

Any one heard of similar? I will try to re-install every module, to see if it helps.
Any suggestions?