Video not playing in project screen

Hello Ive put some photos and videos in my timeline and have gone back and forth checking and editing which was working fine, but after a while when I try to view in the main project screen I am not getting any images. The timeline is playing and I can hear the videos. I thought maybe it was because I had been working on this for quite a while and so I left it over night (Im just putting a holiday video together). However when returning to this the next day at first it started playing fine but when I stopped to go back to edit Im not getting any images again. Can anyone help. Thanks

Shotcut version number? (Help/About Shotcut)
Operating System?
Screenshot of Shotcut of what’s not showing with the timeline track in view.

I`m using version 18.08.14 on windows 10. please can you tell me how to do a screen shot? thanks

this is the screen shot hope you can see ok

Click on where it says “Master”, what filter do you there?
The little symbol (that I have marked with a red dot) indicates a filter on the master.

clicked “filter” but this has made no difference.

Are you using the 3D Text filter on many clips/images? That might be the problem. You can try to disable or remove some of them to see if it helps.