Audio reconnecting badly after sending a project file to someone else.

Hello, I have a client with which I edit the whole video and at the end I send him a project file with all assets, he connects it, apply the final touches and render the video. We were working like this for a past year. Lately when he opens the project file all synchronized audio files, each piece on the timeline is missing timestamps and is playing from the beginning. Schreeshot attached. 

The weirdest thins is, the last video we did, worked perfectly good, but also the previous one had the same issue. So it's not also all time, which is weird, because all of the edits are kind of saimilarly made and all of them have transcript and captions made in Premire Pro.

I also tried sending him with Project Manager, but it also doesn't work.

What else can we do to make it work? And why is this happening lately?