Ah - the split keyboard. This feature, although still supported by iOS12.x for most iPads, was this totally wrecked by this “upgrade”.
Bugs include loss of password autofill from keychain - and corruption of screen-redraw of the keyboard when switching between landscape/portrait modes (and vice-versa).
Lossing the ability to effectively use Split Keyboard with keychain integration was a killer for me. Having wrecked functionality of one iPad to these issues, my Pro 10.5 has remained at 11.4.1 - and an order with Apple for two new 2018 Pro’s cancelled.
I encourage you to report this problem via Apple Support (link at top-right of this page) and via the Apple iPad feedback channel.