Fail to save Data/ saving incomplete data

URL of experiment:

Description of the problem: We performed a test-run as the experiment was already “running” and the test participant could go through the whole experiment without issue. Data saving and credit consumption all worked perfectly.
Now, real participants (recruited through SONA) started doing the experiment (2 so far) and for one of them, no data was saved at all and no credit consumed even though they got their credits on SONA (which can still be explained by discovering the redirect link and the SONA ID themselves) and the other created only partial data, which is all the more vexing as they also received their credits and saving of partial data is turned off in the experiment.
As a side note: This experiment uses sound - I realize there was a problem with sound files yesterday. However, I doubt it’s the issue, as participants reported to hear the sound fine.
I am very grateful for quick help!
Thank you in advance