I had this same conversation with Live Support and sent @VZWSupport on Twitter a message but this is more detailed.
At home, on WIFI, when I try to send a sticker or GIF its stuck at 'Sending...' and the preview bar doesnt load up and just shows placeholders. Randomly though, it works with WIFI at home.
If I turn off WIFI, it seems to work but when I was at the car wash using their WIFI it worked.
However, at home on WIFI, using Samsung Messages I have no problem sending GIFs or stickers.
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I don't think it is a software or device issue myself. I would check your WPA restrictions or reset your Wi-Fi modem to see if that helps.