Tom
I do know what citric acid is and what it is used for. Sure, I can buy it in 75g tube in the cooking aisle of the supermarket if I wish to pay $2.50 for it, but I'd rather buy a kilo of it for $6 online.....
I grew up with a single rinse machine too that was used in conjunction with a suds-saver. My mother never had washing that was sour either.
However, detergents have changed as has the quantity of water that is used. Additionally, this is not a top load automatic nor high sudsing Tide.
The formula used in OMO here was changed in the last 12 months and, until then I had never had an issue. I've subsequently asked my mother about any lingering odours in her exclusively OMO washed laundry and she has confirmed that there has been something 'no quite right' with a few items. She'd put it down to things not drying properly and had rewashed.
This from a person who has never had an odour in laundry in 49 years of married life despite never owning a dryer and having to rely on however long it takes for things to dry.
I'm not using the vinegar to actually sour the whole wash as is common in a commercial laundry, but rather to attempt to neutralise any remaining alkaline activity that may be present in the last rinse and therefore neutralise the wash itself. And whilst a commercial sour should be washed out, many people use white vinegar in small doses as a fabric conditioner.
Assuming it does turn the final rinse water neutral, it won't affect the machine either.
We shall see, or rather 'we shall smell' how it goes.