I agree 1000% percent. The previous urls probably were not mapped correctly.
"The primary reason I see organic drops when migrating is a poor mapping of old URLs to new URLs. Old URLs should be gathered with a full analytics export of pages viewed over a 90 day period, coupled with a Screaming Frog scan of the "old" platform to the new one. This has to be done BEFORE migrating. Another common reason is a poor transfer of content, which includes titles and meta descriptions."
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