Networking with transnet 900's and AD plc's

I am using a 260 for the master and 06's and 250's for slaves and use MDS Transnet 900's for the radio communication. This was working fine but as the network expanded (up to 29 remotes currently) there are sites that will not communicate even though the radio signal strength is very strong and in direct line of site. Also there is a repeater site with a plc that will not communicate but other remotes using this repeater communicate just fine.
There does not seem to be any good reason for this loss of communication as far as I can tell but about 8 sites total are effected. It just seems like it could have something to do with the master program. I have changed parts to eliminate bad equip and have double checked radio and plc programming.
In the master after every RX and WX I use a set cxxx relay command to prevent simultaneous RX or WX at the last rung there is a reset command that resets all the previous c relays. I have started some dialogue with AD tech support to check my master program.
I did solve a problem earlier by turning the buffer on in the master radio which smoothed out the error rate.

Communication setting is Modbus 38400 8N1
Also using insite6 (radio diagnostic software) I have determined that radio signal strength is probably ok.

Without going into a lot more detail I was hoping someone could give me some idea's or could explain how the radio's communicate which could lead to more understanding of the system.

A radio operates very much like a phone modem, and converts the serial bits to a modulated signal. I'm not familiar with your specific radios, but in general they include buffering for data, and some kind of error checking.

If this is licensed frequency radio you could have an interfering signal from a "gypsy" radio link or unauthorized user on a frequency close to yours. If this is a spread spectrum radio, this shouldn't be a problem.

You could try to lower the baud rate to 19.2 or 9600. This will help transmission integrity, without significantly lowering the communications throughput. At high baud rates the overhead of preparing the data strings and handshaking and so on is more of a factor than the actual transmission rate.

If the same stations are always giving you problems, check the antenna alignment. You should generally have an omni-directional at the master and Yagi directional antennas at the slaves.

If all stations are line of sight to the master, consider eliminating the repeater. It may be stepping on the direct signals from the master or slaves.

In the 205 I use a stage method for communications, instead of the method shown in the manual. This format should be available from the AutomationDirect.com tech support guys.

The radio's are spread spectrum unlicensed.
I have to admit that I found an error in my master program that eliminated about half of my problems and AD tech support found another typo (I have to say that automation direct tech support has been very good to deal with)

The baud rate of the master radio can be set at any speed as long as it matches the master plc this is something I have played with but it did not seem to effect the communication. I think the master sets the speed of the network comm for all the remote radios but the remote radios talk to their rtu's at whatever their matching rate is set at. So by adjusting the master baud rate it adjusts the entire network speed but not the remote radio to rtu speed.

Also I did go and move one of the remote antennas around a bit and discovered that it helped so I am going to make some permanent adjustments that I think will help.

I did try the sample program for the master that came from automation directs website using a counter and sp116 and setup the addtional 2 counters one that counts comm active and another that counts comm error. Haven't determined if this is helping any yet but it is interesting.

Thank you for the input