Good evening, thanks for your question. I am Kas and I will assist you with this.
Obviously, attention to detail in issues such as PIP's are important, as essentially, this report is critiquing another's performance, so errors are not good. However, the omission of the word "likely" is not, in my opinion, so detrimental at to warrant a formal warning and can and should easily be amended. It does not change the position of the company detrimentally.
If this is a first and verbal warning, then object but ultimately, it is the very first stage and providing your performance continues to improve then this will be on your record for 3 - 6 months (the employer should make it clear how long it will stay on your record).
If it is a first written warning, then the process is usually slightly more formal and you would get the right to put your position forward. I would object to the giving of a formal warning given your current personal circumstances and the minimal effect of the omission.
I am sure that your employer is not deliberately harassing you, although it may feel that way. But if you feel that they are, you may wish to speak to your union about raising a grievance.
At this stage, I would not recommend that - although if there is a formal disciplinary meeting about the warning, you could have your union rep attend with you for support.
I hope this assists. Any further questions, please dont hesitate to ask.