Struggling to eat

I am sorry to hear that your Dad is struggling to eat again. 
I do not have a similar experience to share only a comment on your question. 
There will be members in this community who have had radiotherapy and follow up endoscopy. Some for symptom relief and some for symptom relief with a curative aim.  
it is not clear from your question whether you are concerned about disease progression or the endoscopy procedure itself being the reason your Dad is finding it difficult to eat again. 
You may get more replies if you share the  outcome of the second endoscopy. 
All of this aside, I am assuming you will have had the opportunity to pose this question to your Dad’s Oncologist?

Best wishes. 

As Rosiee says, if you are asking about whether anyone has had swallowing problems caused by the endoscopy, I have had 11 (yes, eleven) gastroscopies (endoscopies). I had chemoradiation but no operation in March 2021 and I'm on active monitoring so I had a gastroscopy (endoscopy) every 3 months for 2 years, now I'm on 6 monthly tests - I also had a CT scan or PET scan at the same time. 

After each gastroscopy I have a sore throat and slight discomfort where they've taken the biopsies (and excess wind!), but nothing that has lasted longer than a couple of days. I had my latest gastroscopy last week and it was the same again. I have the numbing throat spray and sedative because I have an iodine dye sprayed on the scar area (to show up any cancer cells) which is an irritant and makes the procedure more unpleasant and uncomfortable. 

If you think the endoscopy procedure has caused problems in the oesophagus then I suggest you contact his nurses.