Try "massaging" (gently!) screen around that region - no joke. Once, I had problem with digitizer, after keeping it in pocket with something making slight, yet constant, pressure on one area. After that, device was recognizing touch in a "biased" way - with offset, heading into said area.

Fortunately, 5-10 minutes of massaging screen relaxed it (sic!), during the process, it gradually become less and less visible (monitored it through MyPaint), until it disappeared completely.
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If above doesn't work for you, replacing digitizer sounds like only one option.

/Estel