As well as + verb-ing

Match the endings

A. He had been documenting a number of processes and workflows as well as liaising between the development team and its internal clients.

B. He documented a number of processes and workflows as well as liaised between the development team and its internal clients.

A is correct. Try inverting the clauses, and you can see that the sentence works equally well this way round:

'As well as liaising between the development team and its internal clients, he documented a number of processes and workflows.'

I cannot explain the grammar of this usage, but as a native English speaker and erstwhile professional sub-editor I know that A sounds idiomatic and B does not.