First I don't know why you swapped the drives around. You really should leave the HDD in the HDD bay and then use the SSD in the carrier in place of the optical drive. The reason this is important is the HD bay has crash guard protection whereas the optical bay does not! So if you bang your system while the HDD drive is in process of a read/write it could damage it.
While I don't see that as the issue here its something you should switch the drives around.
I suspect you're hitting a bad HDD cable issue. This is a common issue with the MacBook Pro's both 13 & 15 have issues.
Lets replace it with a new cable following this IFIXIT guide: [guide|10762] and here's the needed cable: [product|IF161-100-4]. I strongly recommend you place some electricians tape on the uppercase where the cable rests to offer additional protection from the rough aluminum surface.
Also make sure the black plastic clips on the mid plane that clip into the bottom cover are in good shape. If you have one broken make sure the one near the HD is the working one.
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After you've replaced the cable I would strongly recommend you make a full backup and then reformat the HD and install a fresh copy of MacOS. So any corruptions on the drive set is removed.
First I don't know why you swapped the drives around. You really should leave the HDD in the HDD bay and then use the SSD in the carrier in place of the optical drive. The reason this is important is the HD bay has crash guard protection whereas the optical bay does not! So if you bang your system while the HDD drive is in process of a read/write it could damage it.
While I don't see that as the issue here its something you should switch the drives around.
I suspect you're hitting a bad HDD cable issue. This is a common issue with the MacBook Pro's both 13 & 15 have issues.
Lets replace it with a new cable following this IFIXIT guide: [guide|10762] and here's the needed cable: [product|IF161-100-4]. I strongly recommend you place some electricians tape on the uppercase where the cable rests to offer additional protection from the rough aluminum surface.
Also make sure the black plastic clips on the mid plane that clip into the bottom cover are in good shape. If you have one broken make sure the one near the HD is the working one.