Can this ratatouille be saved? I just made a batch of ratatouille using green bell peppers. There is a bitter metallic taste. Is there anything I can do to salvage this batch?

This is what I did. Olive oil was used throughout.

Peeled eggplant,  sliced in chunks, salted, rinsed   

Cut slender young zucchini in same size chunks; Did not salt 

Cut an onion and green pepper in chunks 

Defrosted frozen Roma tomatoes from last year's garden. Rough chopped

Sauteed eggplant , added to casserole dish

Sauteed zucchini with an garlic clove, added to casserole

Sauteed green peppers, onion 

Added last year's frozen  Roma tomatoes to the onion/pepper mix, reduced and added to casserole

(I tasted the tomatoes after they defrosted; no issues there)
Added some Herbs d'Provence, covered casserole and baked.

It is bitter and metallic.
What happened ?
Can it be rescued?

How to avoid this next time?

(I really like fresh made ratatouille in the summer)

Thank you
What you're tasting is likely the eggplant -- eggplants with more seeds can have a distinct metallic taste, and can definitely ruin a dish.  There's probably nothing that can be done for this batch, but for next time:

Look at the bottom of the eggplant when you're picking it out -- if it has a small round indentation, then it's a "male" eggplant and will have less seeds;  if it's a larger horizontal indentation, then it's a "female", and will have a higher seed content (and ruin your Ratatouille).  Once you look at a couple, you'll see the difference -- they're distinctly different and easy to pick out once you know what you're looking for.  Google "male vs female eggplants" and you'll find plenty of pictures of this.

One note: the "male/female" nomenclature isn't exactly correct:  What they call a "male" is an eggplant that was less pollenated and therefore generated less seeds, though the eggplants don't technically have any gender -- but, this is the common terminology used to describe the difference.