Here is a problem that I'm having with my Diamond X700.
Hopefully someone can give me some advice on which antenna would suit
my needs best.

Problem:

My Diamond X700 cost me $400. I'm using it for a VHF repeater
antenna.

The problem it causes is every now and then, I get gurgling noises and
crackling in the transmit and it takes out weak signals.

This problem may stay in a few days and be gone for a few days and
then come back again.

It is not my TX RX duplexer. That was already checked out.
I replaced my coax with LMR400. (75 ft. run)
I have even changed repeaters and get the same results.

Someone told me that the Diamond antennaes are NOT good in repeater
service because they whip around and the rods inside do get broken and
cause problems and will not show a bad SWR. My SWR is fine.

Anyone out here have the same problems that I'm having? Do you have
any suggestions on a proper antenna to use?

I do have one suggestion and that was to get a Decibel products DB 224
antenna. Their website shows it as 6 DB gain where my Diamond is 9
DB.
I'm afraid that I will lose my receive coverage with the lesser DB
gain.

Can anyone comment on the Decibel product? Any help and suggestions
would be appreciated.

Or if you can suggest any other antenna that could be used for
repeater use at my home.