Considering https://dictionary.cambridge.org/grammar/british-grammar/could (point "Could + smell, taste, think, believe, etc."), I assume that one is allowed to use "could" to refer to single achievements in the past when the sentence is in the passive voice.
The probability of obtaining suboptimal solutions could be lowered by simply making the optimiser search more but similar waveforms
is better than:
The probability of obtaining suboptimal solutions was able to be lowered by simply making the optimiser search more but similar waveforms
- obviously, only the context helps the reader to know that "could be" does not mean "is likely to be/may be". In the sentences before this one, I used exclusively simple past, so the tense should be clear in my humble opinion.
- the latter sentence also causes a problem since "able" is used for a thing, which is usually reserved for living beings (at least in standard English as far as I am aware)
For me, "be" is also a stative verb like "smell, taste, think, believe" mentioned in the Cambridge article. I know that I can rewrite the sentence and use phrases like "it was possible" or "one managed to", but I would like to avoid these here.
So am I right in thinking that one can use "could be" in the passive voice to mean "was able to be", which sounds awkward?
PS: I am already aware of this article here: "was able to" vs "could", but it didn't help me in this regard. Help would be much appreciated!