Sink drains fine, toilet water won't flush down easily, have taken toilet off no blockages in topilet itself, have snaked the drain and still problem persists. Could this be an airlock problem?

To be honest, I'm not a plumber, but the same thing kind of happened to us last year. It started with the toilets being hard or slow to flush, then raw sewage slowely started coming up in the tubs. I snaked the toilets and everything. What happened was where our sewage line runs into the city sewer system at the street, apparantely grease had built up at the Y. It blocked our sewage from getting into the main sewer. It backed up into the tubs. The city came out and snaked the sewer from our house to the street and knocked the blockage out.
Might help, good luck