2 identical Aspire 1's 5x disk performance difference A114-32 COX3

Hello there,

I bought 2 Acer Aspire 1's model A114-32 COX3 in 2019 and I've noticed recently that the performance of the disk in one is almost 5x faster than the other. The laptops are identical models and even have the same date of manufacture.

The poor performing one has Crystal disk of:

Where as the snappy one has:

At one point I booted Ubuntu from an external disk from the now slower laptop, other than that I cannot think what other changes have taken place that would cause this. I've bee through the usual optimisation but the performance is still poor. Can anyone suggest how to get it back to its former glory?

Thanks for looking,
Bob