Thanks for the reply!
The main version I've been using is v 11.03, which had been working until last night.
Then, I've tried all the different versions I've found in this forum to try and fix the issue.
The newest version 11.08 has not fixed the issue either.
I've tried all the different advice I've found as well, except clearing the cache. I'm getting the following message: 'No cache files were deleted. Either some cache files are still in use or there were no cache files to delete.'
I'm sharing the project: https://drive.google.com/drive/folders/1DmqOXfAVdhmc10TXdhdWosA5tsdbj_oY?usp=sharing
The result I'm getting is that in the exported file with H.264, after the first video from my timeline plays, the same one starts playing again (the snowy landscape opening shot) and the following ones from my timeline never play, until the last one (the green outro screen).
The exporting process only takes a few seconds, which seems strange, compared to the export time in the past or in other video editors.
Any help will be appreciated!