When keyboard issues are limited to keys in the same horizontal row or (slightly diagonal) column, that suggests a physical problem with the keyboard itself, which is built with a grid of rows, a grid of columns, and a grid for keypress detection.
These sorts of problems are limited to the physical keyboard itself, but are generally NOT repairable. a complete fix would be a repair-by-replacemnt of the assembly.
On Macs as recent as the MacBook Pro 15-in 2015 models, the Field-replaceable assembly consists of the keyboard, trackpad, battery, and the top-plate to which all are attached. No smaller sub-assemblies are available. Has your MacBook Pro 15 been checked for battery recall?
15-inch MacBook Pro Battery Recall Program - Apple Support
A work-around (and may be helpful for diagnosis as well) would be to connect a USB keyboard or Wireless keyboard. You will likely find an external keyboard has no issues.