devtool build fails the second time

Hi,
I want to use `devtool modify <recipe>' to modify the source code and create patches. <recipe> already contains some source patches.

My workflow looks like this:

devtool modity <recipe>
Fetching, Unpacking, Patching
all works

devtool build <recipe>

devtool build <recipe>
fails during compile task, that's expected and that's the reason i want to create the patches.

A second
devtool build <recipe>
call, immediatly after the first one fails with
do_fetch: Taskhash mismatch 5786499f8bbbc5af0471f764b7796c77 verses 919d46a764e4f9122d53f1b74d37a4b8

The same taskhash error happens for the do_patch task, with different hash sums.

The do_patch task fails with the error, that the patches have already been applied.

what am I doing wrong?