IBM is competing with Palantir via a product called Analyst's Notebook, which they bought from a company called i2 a while back. Prior to the buyout, i2 sued Palantir over how Palantir's "import from Analyst's Notebook" functionality had been implemented.
It's entirely possible that there are other things going on between Palantir and IBM, but I'm not aware of any other specific squabbles.
Disclosure: I worked at Palantir from mid 2009 to early 2014 and still own some stock.
To be clear, the suit that i2 filed alleged that Palantir stole trade secrets and requested that the suit move forward under RICO law (an anti-Racketeering law meant to fight organized crime). The judge agreed and Palantir settled almost immediately after. i2 then sold to IBM almost immediately after that.
The employees on Palantir's side who were involved also kept their jobs. That sends a really powerful message about who they are.
Beyond the AN issue, there is a wider dispute around the DCGS program for the US Army. Palantir sold point solutions into US army airborne units and the marine corp, earned the respect of the intel analysts and delivered value quickly. Meanwhile the lumbering DCGS 'program of record' implemented by IBM was blowing out the schedule and the budget with meagre effective returns. When other US army units wanted to procure Palantir, they were blocked and redirected towards the failing DCGS program. Palantir cried fowl and sued ....
It's entirely possible that there are other things going on between Palantir and IBM, but I'm not aware of any other specific squabbles.
Disclosure: I worked at Palantir from mid 2009 to early 2014 and still own some stock.