Google Cache Pages not showing full version of website

Hello everyone, I am experiencing a steady drop in organic traffic & impressions since May for one of the clients. The drop is not limited to a particular page or keywords - it is across the board. I also found that the Full version of Google Cache is not loading. It is just a blank page. However, the text version is loading properly. In GSC, the URL are indexed and there are no errors. What can be the reason for the full version not getting loaded? Should I be concerned about this? There are HTML validation errors (including a fatal error) but they are present on my other website as well without any impact. Would really appreciate any thoughts/insights on this.