My brother sewing machine LS2400 The reverse lever is not working. Its loose, meaning that i can't use the sewing machine. When i open the machine its like a metall pice is missing. What should i do?

SOURCE: Reverse lever

lever must be locked in. if possible, you must open it and try to look for something blocking it. maybe a faulty spring or something.

SOURCE: buttonhole lever

If you remove the cover on the upper left portion of the machine, while looking from the left to the right.....Above the BH lever area, you will see a round cam with a post through the middle. Rotate the round can ( with fingers on it), and try again. This will change the angle position on the lever, and hopefully correct your problem. You may have to go a couple of clicks in either direction.

SOURCE: Janome Excel 5124 reverse lever

If you pull the bottom off the machine (half a dozen screws) there is a cam on the main drive shaft. The cam is probably jammed in the reverse position due to lack of lubrication on the shaft. You can move the cam back manually and it will operate in forward direction. It appears that the shaft needs lubrication.

SOURCE: lever is stuck in reverse

If the stitch length bar, which is located on the right side of the machine, is in the up position move it down to where the numbers are. Those numbers are referring to how many stitches the machine will sew in an inch. Therefore, if you put it on 10, your machine will sew 10 stitches per inch. It being up will cause your machine to go in reverse.

SOURCE: brother sewing machine sews in reverse only

you will need to have it serviced sounds like an internal issue with the dial