I suspect that you may be suffering from
Simulcast Distortion. Which site are you using? The Ft Bend Simulcast? Have you tried using the Clodine site instead? Read the linked Wiki page for more details. For simulcast, one of your best options is to use a directional antenna, such as a yagi. Then, aim it, not necessarily at the closest site, but the one that is the farthest away (in direction) than the others. You also can try using the telescoping antenna instead of connecting an external/rooftop one. Then, with the original antenna connected, try moving the scanner to different places in your house. Sometimes a foot or two one way or the other makes all the difference in the world. Also, are there any other transmit towers near you?
Are you using a Favorites list? Or are you using the main database & location? If using the main database & location, what range is set?
While simulcast may be the issue, also be sure that your service types are correct. The scanner ships with the Dispatch types enabled- Fire Dispatch, Police Dispatch, EMS Dispatch, and Multi-Dispatch. You should also enable the corresponding Tac & Talk types- Police Talk, Fire Tac, etc.
There are several members in your county. Hopefully, one of them can suggest other options.