You have to play them back using the same mame version/platform as they were recorded. We've only recently had an inp submitted that completes R-Type (all 8x2 rounds completed).(posted 8690 days ago)the inp link below requires you to play back the game in mame55. It works - I've tried it. Make sure you use the official release from http://www.mame.net of the game engine, not one you compiled yourself or downloaded from the 'dodgy brothers'.
http://marp.retrogames.com/inp/tkx_rtype_1171800_win55.zip
Cheers, Tim