I’m using the latest version on an iPad Pro, but I’ve had to just settle for using another text editor and copy-pasting into Scrivener because the scrolling is killing me. Every time I try to select any text, it scrolls wildly to the end of the file. No matter how carefully I try, I can’t get more than a couple of words selected before scrolling goes mad and can’t be stopped. I’m not having this issue with any other text app.
I use scrivener on my desktop, so I keep using the iPad version to stay in sync, but the inability to select text reliably makes it essentially useless for editing.
See the following post link. Note the ETA material—before using the arrows the initial selection should be made with the selection tool in the extended keyboard row.
https://forum.literatureandlatte.com/t/using-the-select-tool/37821/3
Also see the post immediately following the one I linked to. AmberV has added info about zoom’s effect on the selection tool.
Best…
I’d like to add that I’ve found this sort of scrolling… challenge in other iOS writing software, specifically Bear, iA Writer, and Ulysses. I’ve even had it happen in Safari and Firefox when writing a particularly long post… 
It would appear to be a problem with iOS, an onscreen keyboard, and a small view into a large amount of text.
If I use a hardware keyboard, I can use the usual keyboard selection tools and the issue doesn’t come up unless for some reason I switch to trying to select by touch. But there it is, the out-of-control scrolling is not unique to Scrivener. But the arrow button selection mode workaround is unique to Scrivener.