Air bubbles and trouble flushing

[track32drummer]

The bathroom in my basement is below street-level, so it drains into a basin in the crawl space that is pumped up and out once it gets so full. About a month or so ago, I started to notice large air bubbles coming up through the toilet. Also, the toilet started being finicky when it comes to flushing (it varies based on how full the basin is). Sometimes it will flush like normal, sometimes it drains slowly, and other times I have to run water down the sink or shower to get the pump to kick on before the bowl will drain.

I've already used a plunger on the toilet multiple times, but it doesn't seem to make a difference. Also, I haven't noticed any drainage problems with the sink or shower on the same lines. Any tips to get the toilet back to where it flushes normally every time and stops giving off these loud air bubbles? Is this a seriously problem that could cause or indicate more damage?

All help is appreciated. Thanks.

[DFBonnett]

Sounds like the float in the effluent tank is hanging up.

[track32drummer]

The tank/pump has an alarm on it to warn of malfunction, and it hasn't gone off. I even tested it to make sure it was working. I got into the crawlspace to see if I could notice anything that may have changed, but I couldn't see anything from the outside. The tank is sealed, so I can't tell what's going on inside (nor do I feel like finding out firsthand).

Do I have any options before I call a plumber? Perhaps snaking the toilet or shower? If there is any build-up in the line or in the tank, is there any chemical or septic bacteria I could flush down the line to take care of it?