Hi Mariana,
You can check which index file the web version used (from the results page: follow the "Submission #####" link to get to the submission status page, and look for a line like "Field 1: solved with index index-202-06.fits." Mapping from the 200-series to the publicly available 5200-series is a bit messy :)
Another thing you can do is re-run solve-field, passing in the wcs file with the --verify argument.
I would check the "-indx.png" (red/green circles) plots. You might find that the circles and well matched in one part of the image and then drift apart. That might mean that the "tweak" (polynomial distortion) order has to be increased.
cheers,
--dustin