When on IOS, in any chat, you tap the sticker button, and on the top, you are presented with a list of your packs going left to right. After scrolling left or right, the bar gets larger to give a better preview however nothing is selectable after you initiate a scroll in either direction.
Once you have initiated the scroll you are no longer able to click on sticker packs.
The app allows to tap click on sticker packs after scrolling.
Telegram iOS 8.8.1 (23747), iPhone 13 Pro, 15.5