Basic sergers are not designed for diapers, inserts, nursing pads or thick heavy layers.
Do not blame the equipment when you use it not as it was designed to be used. This is one of the most common complaints about the Brother 1034d Serger and it is nearly always User Error, not equipment malfunction.
Here's a common complaint on our Brother Serger User Support Group:
"Getting ready to throw my brother 1034d serger out the window..... this is the 3-4 time I have had to reset the timing on it..... what is everyone’s suggestions for a reasonably priced decent serger?"
It is very possible this is going to happen no matter what serger you choose if you are using the machine to attempt thick layers.
The Brother 1034d family of sergers are designed for garment-construction and they really do work fine for that purpose. When people throw their timing out three times in a row - it is usually through not using the machine as it was designed. If you need to do diapers, inserts, nursing pads or thick heavy layers - a higher end machine with more powerful engine torque is what you need.
Just buying a more expensive serger is not going to solve the problem. Common sense would suggest that you need to
1. review the technical specifications of the machine before you purchase it, and
2. make sure you understand what you are paying for, and
3. specifically how it is designed to be used.
Some folks are having better luck with mid-range Juki Sergers and that might be a workable solution for diapers, inserts, nursing pads or thick heavy layers. Test the model you are considering with the type of items you are expecting to serge.
Bring some diapers, inserts, or thick heavy layered items with you to the test-drive of the serger you intend to buy. This should give you a reasonable expectation of what the equipment performance will be like.
Once you have chosen a serger, it is your job to learn how to use it - and read the directions. Make sure you understand the directions to avoid breaking your new equipment in the first week of owning it. If it has been a long time since you used the serger, get the manual out and read it again.
Take the time to learn to use your machine correctly and it will last you a long time. Really it is not the equipment's fault if the owner does not follow the directions and does not choose to care for the machine.