The salary has been stagnant or reduced since 2014? Interesting.
While I can't comment on the 20D salary band in the Northeast area at all... It is not uncommon for companies that have a salary reference grade and then defines areas based on a number of factors that represent cost to keep things stagnant for some or all bands in an area. For companies that will share "target value" information, or other benchmarks with respect to a band, with employees (which is nearly every company with such a structure), actual reductions are not common, however.
In some cases, stagnation (or near-stagnation) is an intentional strategy to control cost and/or realign compensation with a specific (lower) target in mind.
In other cases, it's just a case of internal politics making it a generally unfavorable and/or very difficult thing to adjust upwards. In this case, no wise career-focused employee would want to adjust the pay band in terms of an increase until the negative effects of not addressing the stagnation tip the political calculation in favor of taking action.