The Scottish Qualifications Authority came as close as it dared this week to reassure politicians, parents and pupils that their summer would not be ruined for the second year running by incomplete, missing or inaccurate exam results - but without committing itself to “the g-word”.

Bill Morton, the SQA chief executive, told MSPs during their latest grilling in the Parliament’s education committee on Monday that the organisation had consistently taken care to avoid being drawn in to giving guarantees, but he added: “The prospects of a successful certification on August 14 are there.”

In a further cautious note of confidence, John Ward, the SQA chairman, told a press briefing last week: “we have passed all the checkpoints in our action plan to date and that is a significant reassurance. To this point, we have no showstoppers.”

If the SQA does not like guarantees, it also tries to avoid being pinned down to precise figures which might frighten the horses. But MSPs teased out of the officials who appeared before them this week figures which showed surprising data gaps, given that schools had to submit information to the SQA by the end of May.

The authority insists it is on top of the problem, which prompted the observation from Michael Russell, the SNP’s education spokesman, that these revelations about missing deadlines, missing data and the rhetoric of assurances were beginning to sound “eerily familiar”.

The figures show, however, why the SQA is being cautious about them: it is their shifting rather than their precise nature which is the problem. The authority revealed to MSPs that there are 58,000 entries for the internally-assessed course units for which the SQA had not received any results by June 11. The figure had fallen to 47,000 by this week. The SQA says it may never receive many of these results because the candidates had not taken the units.

Billy MacIntyre, the SQA’s director of awards, said there are 37,500 units affected by anomalous data in the school sector out of 800,000 units for whih a result could be expected. “The numbers are not significant, they’re not a cause for concern and we are confident that they are reducing as we speak,” he said.

There were also 13,107 course and exam entries for which there was missing or incomplete assessment data on June 11, the SQA added. This figure was also expected to fall.

Mr MacIntyre said the vast proportion of these were Christmas leavers whose departure had not been notified to the SQA by schools. Anton Colella, the depute head at St Margaret Mary’s Secondary in Glasgow, who has been seconded as an external director of the SQA, told the committee that teachers are reluctant “to put a full stop” on Christmas leavers in case they eventually turn up and sit the exam.

The SQA has already run two checks on the information it holds from schools and a final “closure report” will be sent to schools next week to ascertain whether the exam data is correct before the start of the holidays.

This is a new procedure which did not exist last year and was one of the reasons cited by Dennis Gunning, the SQA’s director of development, for having greater confidence in a successful exam diet this year.

Dr Gunning, the only surviving SQA director from last year, told the education committee that its knowledge of the data was “hugely better” than last year, which was dependent largely on guesswork. The process of preparing for the exam, such as the appointment of markers, had also improved and the organisation was “systematically planning for contingencies when things go awry as they always do in an operation of the scale that we run,” Dr Gunning added.

Mr Morton said another difference from last year was that staff were more confident in reporting problems. “We can only fix what we know about,” he said to the MSPs.

Mr Colella told the committee: “We can say, speaking for the centres, that we know the state of play. We couldn’t say that last year and people should find that a reassurance.”

But he added: “Schools also have to look at how they handle the arrangements for the exams so people are not faced with disputed data late on in the session.