(edit3 - 10-19-2020) Were you searching a folder or a single engine when you observed the problem last? I've uploaded v1.27.5 which fixed the same problem v1.27.4 did, but when searching a folder as well.

(edit 2) Thanks for the reply. I thought the bug fixed in 1.27.4 would take care of your issue, but there must be another bug. I've tried all the engines you mentioned, but I'm getting good search results using the context menu now. Could you open ContextSearch options -> Search Engines and tell me if you see an orange (FF) next to those engines you're having issues with? If not, could you edit one of them and paste the template / method / etc info? It could help narrow down the problem.

(edit) Nevermind, version 1.27.4 going up. Context menu was not working with Firefox engines

Would you mind opening a ticket at the support site or editing your reply here? Some users seem to be experiencing problems with the latest builds and I could use some input on what exactly is going wrong. I tried adding Yandex to my install and had no problems, and troubleshooting is difficult when I can't replicate the bug.