SPSS Statistics

I have some fairly small data sets (~275 total cases) in an educational context built on 7-point Likert-type Scales. I'm looking at two different types of instruction of the same material and want to find out if the results are similar or different. Since the material is basically the same I would expect similar results but t-tests show generally lower results for one group. I wanted to see what Bayes Independent Samples would offer, and I am finding less evidence for differences, but oddly, the items where the groups have the largest differences in means are showing the lowest Bayes factors. I understand this to mean that these are showing "very strong" and "extreme" evidence for the null hypothesis, i.e., that the two groups have the same results. I even note for these items that the lower group's mean falls below the "95% Credible Interval" that shows up in the "Posterior Distribution Characterization for Independent Sample Mean" that is part of the SPSS output. Am I understanding this correctly? Is there something I did wrong?  Any insight would be appreciated.

Thanks!