This sounds like a control board failure, as its losing track of how long to spin for.
Unfortunately this will require an engineer visit, to rule out any other sensor fault.
There are no other tests you can perform, other than set the washer to spin only and see if it starts and completes the cycle without issue.
If you would like me to recommend an engineer in your area, please provide a post code.
How did you get on?
This would have likely occurred if an engineer attended site, its unfortunate but at least you have not had to go to the expense of having an engineer attend site.
Please note you can buy replacement counter weights, but the cost combined with that of the control panel would probably make it uneconomical to repair as you suggested.