Fixes for robot diagnostics signal test

- Do not refresh positions right after end of motor movement test
- Before refreshing positions, make sure to update position estimation to avoid API errors

hardware-testing/hardware_testing/production_qc/robot_assembly_qc_ot3/test_signals.py

@@ -117,7 +117,6 @@ async def _do_the_moving() -> None:
         move_coro = _do_the_moving()
         stop_coro = _sleep_then_activate_stop_signal()
         await asyncio.gather(stop_coro, move_coro)
-    await api.refresh_positions()
 
 
 async def run(api: OT3API, report: CSVReport, section: str) -> None:
@@ -152,7 +151,9 @@ async def _home() -> None:
         await _move_and_interrupt_with_signal(api, sig_name)
         if not api.is_simulator and "external" in sig_name:
             ui.get_user_ready("release the E-STOP")
-        stop_pos = await api.gantry_position(mount)
+        if "external" in sig_name or "estop" in sig_name:
+            await api._update_position_estimation([Axis.X, Axis.Y, Axis.Z_L, Axis.Z_R])
+        stop_pos = await api.gantry_position(mount, refresh=True)
         report(
             section,
             f"{sig_name}-stop-pos",