FilterObjects problem: IndexError: index is out of bounds

Good afternoon,
I’m running CP2.2.0 and in my pipeline I’m getting (every ~100-200 images) the following error in FilterObjects:
IndexError: index 2 is out of bounds for axis 1 with size 2
The traceback is:
Traceback (most recent call last):
File “cellprofiler\gui\pipelinecontroller.pyc”, line 2826, in do_step
File “cellprofiler\pipeline.pyc”, line 2067, in run_module
File “cellprofiler\modules\filterobjects.pyc”, line 469, in run
IndexError: index 2 is out of bounds for axis 1 with size 2
Would anybody have any idea what this error means?
I cannot identify a consistent difference between the images that run smoothly and those that fail.
Thanks very much for any help
Best
Carlos