Japanese 6.4 discrepancy.

In lesson 6.4 there is a discrepancy between the conversation in the lesson audio and in the conversation audio. In the lesson audio they say and explain....shitai desu. Which is fine. But in the conversation audio it is ......shitakkata desu. Its not explained & I don't understand that; it doesnt seem to be part of suru & looks more like a past tense adjective; obviously some bit of grammar Ive not seen yet. Can someone resolve the discrepancy & explain the second form please?

The admin of the site should resolve that problem. On the other hand, about the 'shitakatta', it isn't so difficult. The 'want to do' suffix is ~tai. Cut down the last 'i' and add ~katta and voilla, you get the past form => 'wanted to do'.

Many thanks; I'd not encountered that to put -tai into the past tense, although I'd guessed it was a past form from the similarity to adjectives. (Actually I dont think we've met past tense adjectives at this point in Rocket, but I have elsewhere.) Much appreciated.

The ~tai actually makes the verb into a i-type adjective. So you can do all the things with it that you could do with any other i-adjective. Just for example: "Nomitakattara" = If (I) want to drink. "Tabetakunai" = don't want to eat. That ~nai part is another auxilliary adjective, so then even "Chijimitakunakattara" = "If it doesn't shrink." can work.