[SteveCG]

If you say recordings made on other tape recorders play back correctly (your first post did not quite make that clear) but recordings made on the Akai occasionally sound dull on only the right hand track then it is possible that either your Akai has a RHS recording bias-level problem or that there is intermittent problem in the RHS replay stage of your Akai. Does the intermittent dullness happen at the same places on the tape when replaying?

By the Way: can you try playing a recording made on your Akai on another machine? If you can then does it sound alright at points where the Akai sounds dull?