I use Routeway Moose with Saddle 2 cost. However several times I have been unable to use the Saddle ability after playing a spell on my first main step (using all my mana, so can't cast more spells), and the game goes directly to the declare attackers phase where I can't anymore use the Saddle ability even though I have available creatures to Saddle (at sorcery speed). So I think it is a bug in the Saddle mechanic, where it does not query if I want to use it before attackers are declared. Please fix the bug!

I use MTG Arena on Android, with latest updates. No screenshot from gameplay unfortunately.