In the log I saw records of the following form: Set Buy order: FAIL; Status: 400 Limit price can’t be higher than, but I don’t have orders placed, what kind of error is this?

If you have such an error in your logs and orders are not placed, it means that the exchange does not allow you to set an order higher than your strategy wants.
For example, you have the following entries in your log:
1) Task 342 started; USDT-XVS (strategy ) UseAsk: 7.9260 CurAsk: 7.92360 BUY 10.405
Task #342 started: on the USDT-XVS pair (strategy named “ST-NEW”) at the current ASK price of 7.9260 a limit buy order must be placed high in the red glass on the 10.405 price line (i.e. +30% of the ASK price)
2) USDT-XVS Set Buy order: FAIL; Status: 400 Limit price can’t be higher than 9.134430
It is impossible to set a Buy order on USDT-XVS pair (the task has failed) because of the error “Status: 400 Limit price can’t be higher than 9.134430” (or not more than +15% of ASK price)
3) === FAILED TO SET BUY ORDER ! vol.4.80000000 price: 10.405 total 100$
The result is the following entry: BUY ORDER CANNOT BE SET AT 10.405 price line – order size 100$
In this example, in the strategy settings, the buyPrice=30 parameter was set (to set a limit order of +30%) and the exchange has at some point set a limit and did not allow you to set an order higher than +15% (according to the log entry). In this case it is necessary to decrease the value in the parameter buyPrice from 30% to 15% or lower. What exactly the restrictions introduced by the exchange, in each case, you can see in the log: check the current ASK price and the maximum allowable value of the price above which the exchange does not allow to expose the limit order and then adjust the settings of the strategy.