This looks like a bug in "Products.SQLAlchemyDA" (it is unlikely that the product exposes a manage_addTextIndexNG3). Maybe, you got a different version in your Plone 3 environment -- one that did not yet have the bug.
I recommend that you check which versions of "Products.SQLAlchemyDA" are included in your Plone 3 and Plone 5 environsments, respectively. If they are different, use so called "version pinnung" to force the use of the same version.