Being able to import my previous tracks into the GPS Recording was the primary reason I held off on subscribing to the new version.
The subscription has a free trial period, so you can check if it works for you.
Can you post the saved gpx file, so we can check your report and if the file is valid?
Local tests show the export / import processes with any options to work correctly.
This looks like a huge file (how many km?).
For best performance it is recommended to save + clear GPS recording from time to time.
(especially if the recorded track appears on the screen)