When Gaia spawns it textures it "travels" across the terrain to process the texture changes on the splatmap (The splatmap is an image file in the background that stores which texture is applied where on the terrain). When a grid-like or "dotted" pattern appears on the terrain, it usually means that the spawner is taking too large steps / increments when traveling and therefore creates an ugly gap pattern on the splatmap.
To fix this, please review the following settings on the spawner component:
Location Selector should be set to "Every Location" and "Location Increment" needs to be set up in such way that the spawner hits every pixel on your splatmap so that there are no gaps when traveling. To find out the best value, you will need to set it according to your terrain width and length, and control texture resolution. Examples:
If your terrain has a width and length of 1024 and your control texture resolution is 1024, the Location Increment needs to be 1
If your terrain has a width and length of 1024 and your control texture resolution is 2048, the Location Increment needs to be 0.5
If your terrain has a width and length of 2048 and your control texture resolution is 1024, the Location Increment needs to be 2
and so on. Basically you divide width and length by control texture resolution. If you have a non-square terrain you can take the smaller of the two values width / length for the calculation. After you adjusted that, there should be no more ugly patterns when you spawn the textures again.