This overall I believe is an amazon thing. They have been rewriting their websites and Conor has had to scramble to keep up with the ever changing API's (Application Program Interface). Also amazon has changed the rules regarding the use of API's in that each referral agent (Bruji in this case) must forefill a minimum monthly referral quota for each amazon country site.
Good Will Hunting (ASIN: 1558908641) [
https://www.amazon.com/Good-Will-Hunting/dp/1558908641?tag=pedia01-20&linkCode=osi&th=1&psc=1] provides very minimal info, including no Release date.
But if I use ASIN: B004UGAMSK [
https://www.amazon.com/Good-Will-Hunting-DVD/dp/B004UGAMSK/ref=tmm_dvd_swatch_0?_encoding=UTF8&qid=&sr=] I get far more information. But here is the thing, the release date is on the amazon site but DVDpedia is not picking it up.
Then if you search for Skyfall (ASIN: B01DJ63UJY) in Amazon US, then Amazon CA, then Amazon UK, each separately, you get different results.
If you search using the Title you get multiple results. If search using UPC you will get a different result again. Then you have to worry about private sellers where each copy of the DVD has a different ASIN.
AND you will end up again with different results for Blue-ray, 4k and multi-format disks.
Finally if you are cataloguing a Title as Streaming Media you get results that the pedia's are not
yet designed for.
So all up what have we learnt. First up this must be driving Conor at Bruji absolutely crazy. Next I would just use the UPC number (barcode) for your country amazon site, then gather the remaining info from IMDb and then if necessary manually fill in the missing info.
I hope this provides at least a partial explanation for your query.