The pack opener can possibly attributed to switching our images from the revealed cards back to our native server instead of our Google Cloud Hosting. This was done to reduce cost. With the amount of packs being opened our Google Cloud Server was rising in cost each month (hundreds of euros). However the good thing about Google Cloud is that it's must faster/responsive and the server is closer to many of the users on the site. If we had more people turning off ad-blocker we could alleviate this somewhat.
I don't want it to be a problem though so I'm going to swap it back to using the Google Cloud images in a couple of minutes since you aren't the first to complain since the switchover.
For the collection manager, I'm not happy with it either. I have a big overhaul planned that I have rolled out on https://digimoncard.io
whcih both load the collection manager using the excellent jQuery datatables. This makes it fast and responsive even on large collections.
I plan on fully migrating this over to YGOPRODeck in the coming week or two.
Sorry about the issues you have been having!
Owner of YGOPRODeck. Please PM me for any issues regarding the site.