So here is my scenario and not sure if anybody else has experienced this or not.
My Steam Library is very large, over 20k and climbing.
I use Augmented Steam to help filter out tagged vs. untagged games/apps.
I basically tag everything NOT in my library as on my WISHLIST, which is now nearing 180k
I use Augmented Steam to go through newest/newly released titles and sub-sort by the GAMES category and then Free.
I then filter using lowest price, but can filter by release date or relevance etc.
I then go by page instead of infinite loop so I can see pages of 25 items at a time.
As I go through hiding the games already in my library I will get a blank page instead of showing the next page on the list, it is pretty random as to when this occurs but when I force a refresh in the browser using F5 I get an HTTP 429 error, this seems to indicate TOO many requests.
Not sure if the Steam Client does the same as I use Augmented Steam extension in Google Chrome.
I will do some testing within the Steam Client to see if the same thing occurs.