Breaking down work works great until the breakdown is unknowable. Things like research, that require creative experiments to POC things that are not known apriori. That’s when task breakdown breaks down.
"spend 3 hours on investigating X, 3 on Y, 3 on Z"; and then have a planning session about what to do next.
You have 4 outcomes - the first one solves it, the second, the third or none.
If it is solvable with mild effort, you have a 50% chance of solving it by attempt 2/6 hours.
And at some point, you just gotta do it.