Working with Refinitiv Data Python library I have some bond titles for which I pull the Ultimate Parent Id in order to further query some data:

>>> import refinitiv.data as 
>>> import pandas as pd

...

>>> ParentIDs   
        Instrument Ultimate Parent Id
0     US013822AC54         5051045063
1     US013822AE11         5051045063
2     US013822AG68         5051045063
3     US013822AH42         5051045063
4     XS2342910689         5057937159
...            ...                ...
3238  US98955DAA81         5053129374
3239  XS2431015655         5053129374
3240  US98980BAA17         5043459833
3241  US98981BAA08         5041798671
3242  US98980HAA86         4295893641

[3243 rows x 2 columns]


>>> ParentIDs['Ultimate Parent Id'].unique().dropna()
<StringArray>
['5051045063', '5057937159', '4295903254', '4295901827', '5083796424',
 '4298089043', '5038907093', '4295906590', '5000065666', '4295900267',
 ...
 '5069399010', '4295908523', '5042953645', '5067514871', '4296579444',
 '5082038238', '5053129374', '5043459833', '5041798671', '4295893641']
Length: 1431, dtype: string

However, if I pull the Primary Quote, I get the following error:

>>> RICs = rd.get_data(
...   universe = ParentIDs['Ultimate Parent Id'].unique().dropna(),
...   fields = ["TR.PrimaryQuote"]
...   )
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Users\...\AppData\Roaming\Python\Python311\site-packages\refinitiv\data\_access_layer\get_data_func.py", line 126, in get_data
    raise RDError(-1, except_msg)
refinitiv.data._errors.RDError: Error code -1 | Backend error. 400 Bad Request Requested universes: ['5051045063', '5057937159', '4295903254', 
'4295901827', '5083796424', '4298089043', '5038907093', '4295906590', '5000065666', '4295900267', '5082539928', '5063764430', '4295863289', ...

At a second attempt it worked.

1. What does this error message mean?
2. Is the API "fragile"? It also takes sometimes a very long time just to get some data (e.g. "Ultimate Parent Id")