Have you got the cap irons and bolts for the cutter block?
There won't be any wedges on this baby!
Firstly,if both the cap irons are off then you ought to clean them all up and balance them, using a balance, the slight difference in the weight of the bolts will help by changing them around.
If one iron is off then don't get them mixed up at all, work on 1 side at a time and mark the block and the correct cap iron with tippex.
Any Vibration is to be avoided as the consequences can be dangerous, I've seen it!
Should the bolts be tight in the threads, then swap them about . Do NOT force them if they are tight.
Measure the old cutters, if the cap irons are rebated, as i suspect they will be, to get the right cutter thickness, again this is obviously very important.
Find a good saw doctor or saw shop and get their advice as to size in thickness.
Also tell him that this planer will rebate, see the cutter block bearing is ground off, below the bed height, I'd say about 3/4", or 19mm, so a light touch on the grinder with the new blade end, and set the blade 1mm over the block, but missing the bearing housing.
Blades Too thick or too thin, will have the same outcome, flying steel!
There ought to be some name cast on the machine body, or at least some name or model. To help you.
HTH Regards Rodders