I just had to write in support of TerryE's position: abandoning Calc over failure to rename sheets sounds like an extreme move.
If there is a way to resolve your concern, the dedicated volunteers in this forum will find it and share the solution with you - and all other Calc users. If this is an application defect, then at least the issue will be brought to light and a remedy sought. Either way, we all benefit.
I (again) wish to go on record thanking all the volunteers who share their time and expertise helping the growing OOo community. They are an excellent group!
LO 5.x on Linux Mint 17.3 Cinnamon
A candle loses nothing by lighting another candle.