There are no issues IF handled properly. Working clean, freezing in packages with the greatest surface area possible, ONLY defrosting under refrigeration and working sausage in smallest batches possible keeping the bulk of the meat to be ground/stuffed cold until needed. Most concern comes from the fact that freezer temps do not kill bacteria it only inhibits growth. Additionally at refrigeration temps 34*F to 38*F bacteria still multiplies albeit very slowly. So, many people fear multiple thaw and freezing generates more bacteria growth then they are comfortable with. Beyond this multiple thaw and freezing will eventually cause the repeated formation of ice crystals to breakdown the texture of meat making the final product mushy and have a dry grainy mouth feel. Buy and freeze your bulk meat and fat and make and freeze your sausage once without concern. The following is taken directly from the USDA Fact Sheet on Freezing and Food Safety...
Refreezing
Once food is thawed in the refrigerator, it is safe to refreeze it without cooking, although there may be a loss of quality due to the moisture lost through thawing. After cooking raw foods which were previously frozen, it is safe to freeze the cooked foods. If previously cooked foods are thawed in the refrigerator, you may refreeze the unused portion. Freeze leftovers within 3-4 days. Do not refreeze any foods left outside the refrigerator longer than 2 hours; 1 hour in temperatures above 90 °F.
If you purchase previously frozen meat, poultry or fish at a retail store, you can refreeze if it has been handled properly.
I hope this puts all your fears aside...JJ
