I've got a Repetier modified Da Vinci 1.0A which is printing very well except the first layer.

The test strip will print the first half, then it doesn't put anything down for the rest of the test and for part of the first layer. In the middle of the first layer, it will just start extruding onto the bed. I've leveled the bed as best as I can and the areas that don't extrude are not the same part of the bed. Do I need to offset the first layer to give it more room to extrude?

Need picture of first layer before make any conclusion. Also if you don't know the history of this Repetier modified Da Vinci 1.0A, make sure there is no automatic bed leveling setting stored. Repetier modified Da Vinci 1.0A have guided semi-manual bed leveling option, if your bed is wrapped, you should be able to tell during the semi-manual bed leveling process.

I've got a Repetier modified Da Vinci 1.0A which is printing very well except the first layer.

The test strip will print the first half, then it doesn't put anything down for the rest of the test and for part of the first layer. In the middle of the first layer, it will just start extruding onto the bed. I've leveled the bed as best as I can and the areas that don't extrude are not the same part of the bed. Do I need to offset the first layer to give it more room to extrude?

Your bed is probably warped as was the case with most of the 1.0A machines. Your best bet is to get a piece of tempered glass that is 6mm thick cut to the same as the stack glass and place it over the stock glass using the existing clamps. Then use the manual leveling method stickied at the top of XYZ section. It will take longer to heat but give you less of the frustration you have now.

The test strip will print the first half, then it doesn't put anything down for the rest of the test and for part of the first layer. In the middle of the first layer, it will just start extruding onto the bed. I've leveled the bed as best as I can and the areas that don't extrude are not the same part of the bed. Do I need to offset the first layer to give it more room to extrude?