Apologies - that shouldn’t happen.
During early access we have made a major overhaul of internal systems which make very old save games in theory work, but largely result in unbalanced ships.
When we did this, we put information and a warning about this in the update news item.
It’s unfortunately something that needed to happen.
That said, the save games certainly should load - they might just result in loading ships with incompatible configurations.
Can you email us the saves that are not loading correctly?