Complex sentence: They agreed that the scientists'research methods had serious problems which they never corrected, arguing that the NIMH's rationale in rejecting the grant extension should have been a sign of flaws in the scientists' research methods.
Split into simpler sentences: They agreed that the scientists'research methods had serious problems which they never corrected. In particular, they pointed to the NIMH's rationale in rejecting the grant extension, arguing this should have been a sign of flaws in the scientists' research methods.