First line fault

Hello there,
I’m a 3018 pro user. I’ve been using it for about 2 or 3 weeks. but the machine often makes mistakes. that is, he draws the first line incorrectly. then he can draw all the lines in a regular way. what could be the reason for this?
The second mistake is when I cut a circle, each circle is of a different size and I cannot combine the circles. I see a 2 cm difference.
I am using an easel by the way.
Best Bunyamin

Sorry for the late response here, was on holidays.

So If i am understanding correctly, sometimes the machine is off and sometimes it is not. There are a few things to consider here, One is feed and plunge rates, if those are too aggressive it will cause some bending and flexing on the machine causing incorrect carving, also, the first line is usually always taking out the full width of material which can add more stress to the machine, the following carves may be partial bites, meaning that only half or so of t he bit are conntacting the wood giving it less resistance and stress, giving you the correct carve. Make sure all mechanical connections are tight, make sure the spindle is level and perpendicular to the bed.

My guess your feeds and plunge rate may be too aggressive for the machine to handle.

Hope this Helps,
Shawn