Minor revision stuck for 4 months and the journal is not responding
I submitted a minor revision of a paper over 4 months ago, and since then its status in the tracking system hasn't changed at all: it looks like the handling editor hasn't touched it yet, or if he did, he didn't update the status in the system - in any case, I'm in the dark about what is happening. I tried contacting the editorial office several times, and later the managing editor of the journal, but I didn't receive any response. This is for a paper that's been submitted 18 months ago to a highly ranked humanities journal. Both reviews were very positive, with only small comments to address.
Would it be a breach of etiquette to politely contact the handling editor directly at this point, and ask about the status? My concern is that officially, all communication is supposed to go through the editorial office, and handling editor's contact was never explicitly mentioned - I'd have to cold email him through his institutional email (I only know his name from the "minor revision" decision sent by the editorial office). Should I perhaps be contacting the editor-in-chief instead?