Send fails during sync

[jamesob]

Traceback (most recent call last):
  File "/usr/local/bin/coldcore", line 3268, in <module>
    main()
  File "/usr/local/bin/coldcore", line 3259, in main
    cli.run()
  File "/usr/local/bin/coldcore", line 318, in run
    return fnc(*func_args, **func_kwargs)
  File "/usr/local/bin/coldcore", line 2163, in prepare_send
    return _prepare_send(config, rpcw, to_address, amount, spend_from_list)
  File "/usr/local/bin/coldcore", line 2837, in _prepare_send
    result = rpcw.walletcreatefundedpsbt(
  File "/usr/local/bin/coldcore", line 625, in _call_wrapper
    return self._call(name, *args)
  File "/usr/local/bin/coldcore", line 575, in _call
    raise JSONRPCError(
__main__.JSONRPCError: msg: 'Fee estimation failed. Fallbackfee is disabled. Wait a few blocks or enable -fallbackfee.'  code: -4