The unburnt residue from wvo can coke up the rings. Or if the car is not used daily turn to a very strong gum type adhesive in the ring lands. Injectors can get in pretty bad shape from it as well.

I am not a fan wvo myself. It takes some effort for example to even dewater it. I suspect that is what killed so many injection pumps using it in the day. Processing a water component through injection pump elements. Is abrasive in nature.

Anyways I would do a new compression check. If lower than the last time. Do a cylinder soak for about a week. Then recheck compression. Starting with a pull and not with the higher speed starter you have. Is not a good thing.

Of course make certain the glow plugs are really working. The interior light should dim when you apply the glow plugs.